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<!doctype html><html lang=en class=no-js><head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1,shrink-to-fit=no"><meta name=generator content="Hugo 0.98.0"><meta name=robots content="index, follow"><link rel="shortcut icon" href=/favicons/favicon.ico><link rel=apple-touch-icon href=/favicons/apple-touch-icon-180x180.png sizes=180x180><link rel=icon type=image/png href=/favicons/favicon-16x16.png sizes=16x16><link rel=icon type=image/png href=/favicons/favicon-32x32.png sizes=32x32><link rel=icon type=image/png href=/favicons/android-36x36.png sizes=36x36><link rel=icon type=image/png href=/favicons/android-48x48.png sizes=48x48><link rel=icon type=image/png href=/favicons/android-72x72.png sizes=72x72><link rel=icon type=image/png href=/favicons/android-96x96.png sizes=96x96><link rel=icon type=image/png href=/favicons/android-144x144.png sizes=144x144><link rel=icon type=image/png href=/favicons/android-192x192.png sizes=192x192><title>Façade | alguidelines.dev - Business Central Design Patterns</title><meta name=description content="Created by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides (Gang of Four), Described by Jesper Schulz-Wedde (Microsoft)
Abstract
The intent …"><meta property="og:title" content="Façade"><meta property="og:description" content="Created by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides (Gang of Four), Described by Jesper Schulz-Wedde (Microsoft)
Abstract The intent of this pattern is to provide a unified API to a single or a collection of potentially complex subsystems. If you apply this pattern as a general pattern, you will ensure improved:
Decoupling Encapsulation Readability Testability Maintainability Context Whenever you want to write an isolated piece of business logic, from now on referred to as subsystem, this pattern should be applicable."><meta property="og:type" content="article"><meta property="og:url" content="https://alguidelines.dev/docs/patterns/facade-pattern/"><meta property="og:image" content="https://alguidelines.dev/images/og-image-fission.png"><meta property="article:section" content="docs"><meta property="article:modified_time" content="2022-02-24T15:36:06-08:00"><meta property="og:site_name" content="alguidelines.dev - Business Central Design Patterns"><meta itemprop=name content="Façade"><meta itemprop=description content="Created by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides (Gang of Four), Described by Jesper Schulz-Wedde (Microsoft)
Abstract The intent of this pattern is to provide a unified API to a single or a collection of potentially complex subsystems. If you apply this pattern as a general pattern, you will ensure improved:
Decoupling Encapsulation Readability Testability Maintainability Context Whenever you want to write an isolated piece of business logic, from now on referred to as subsystem, this pattern should be applicable."><meta itemprop=dateModified content="2022-02-24T15:36:06-08:00"><meta itemprop=wordCount content="1321"><meta itemprop=image content="https://alguidelines.dev/images/og-image-fission.png"><meta itemprop=keywords content="AL,Decoupling,Readability,Testability,Extendability,"><meta name=twitter:card content="summary_large_image"><meta name=twitter:image content="https://alguidelines.dev/images/og-image-fission.png"><meta name=twitter:title content="Façade"><meta name=twitter:description content="Created by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides (Gang of Four), Described by Jesper Schulz-Wedde (Microsoft)
Abstract The intent of this pattern is to provide a unified API to a single or a collection of potentially complex subsystems. If you apply this pattern as a general pattern, you will ensure improved:
Decoupling Encapsulation Readability Testability Maintainability Context Whenever you want to write an isolated piece of business logic, from now on referred to as subsystem, this pattern should be applicable."><link rel=preload href=/scss/main.min.84a617ff0c0265eb62b5cd2929c572f4ed37dc4907d0cf068be4eb2974f6d60f.css as=style><link href=/scss/main.min.84a617ff0c0265eb62b5cd2929c572f4ed37dc4907d0cf068be4eb2974f6d60f.css rel=stylesheet integrity><script src=https://code.jquery.com/jquery-3.6.0.min.js integrity=sha384-vtXRMe3mGCbOeY7l30aIg8H9p3GdeSe4IFlP6G8JMa7o7lXvnz3GFKzPxzJdPfGK crossorigin=anonymous></script>
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<button class="btn btn-link td-sidebar__toggle d-md-none p-0 ml-3 fas fa-bars" type=button data-toggle=collapse data-target=#td-section-nav aria-controls=td-docs-nav aria-expanded=false aria-label="Toggle section navigation"></button></form></div><div id=content-desktop></div><nav class="collapse td-sidebar-nav" id=td-section-nav><ul class="td-sidebar-nav__section pr-md-3 ul-0"><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child active-path" id=m-docs-li><a href=/docs/ title="AL Guidelines" class="align-left pl-0 td-sidebar-link td-sidebar-link__section tree-root" id=m-docs><span>Docs</span></a><ul class=ul-1><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child active-path" id=m-docspatterns-li><a href=/docs/patterns/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docspatterns><span>Design Patterns</span></a><ul class="ul-2 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child" id=m-docspatternsapi-register-fieldset-li><a href=/docs/patterns/api-register-fieldset/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docspatternsapi-register-fieldset><span>API Register Fieldset</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child" id=m-docspatternscommand-queue-li><a href=/docs/patterns/command-queue/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docspatternscommand-queue><span>Command Queue</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child" id=m-docspatternsapi-delegate-operation-li><a href=/docs/patterns/api-delegate-operation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docspatternsapi-delegate-operation><span>Delegate API Operation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child" id=m-docspatternsevent-bridge-pattern-li><a href=/docs/patterns/event-bridge-pattern/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docspatternsevent-bridge-pattern><span>Event Bridge</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child active-path" id=m-docspatternsfacade-pattern-li><a href=/docs/patterns/facade-pattern/ class="align-left pl-0 active td-sidebar-link td-sidebar-link__page" id=m-docspatternsfacade-pattern><span class=td-sidebar-nav-active-item>Façade</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child" id=m-docspatternsgeneric-method-pattern-li><a href=/docs/patterns/generic-method-pattern/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docspatternsgeneric-method-pattern><span>Generic Method</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child" id=m-docspatternsno-series-li><a href=/docs/patterns/no-series/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docspatternsno-series><span>No. Series</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child" id=m-docsbestpractices-li><a href=/docs/bestpractices/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsbestpractices><span>Best Practices</span></a><ul class="ul-2 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesapi-page-li><a href=/docs/bestpractices/api-page/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesapi-page><span>API Page / Query</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesblank-lines-li><a href=/docs/bestpractices/blank-lines/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesblank-lines><span>Avoid too many blank lines</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesbegin-as-an-afterword-li><a href=/docs/bestpractices/begin-as-an-afterword/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesbegin-as-an-afterword><span>begin as an afterword</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesbegin-end-li><a href=/docs/bestpractices/begin-end/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesbegin-end><span>Begin-End - Compound Only</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesbinary-operator-line-start-li><a href=/docs/bestpractices/binary-operator-line-start/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesbinary-operator-line-start><span>Binary Operator to Start Line</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticescase-actions-li><a href=/docs/bestpractices/case-actions/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticescase-actions><span>CASE Action on next line</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticescomments-spacing-li><a href=/docs/bestpractices/comments-spacing/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticescomments-spacing><span>Comment Spacing</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticescustomtelemetry-li><a href=/docs/bestpractices/customtelemetry/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticescustomtelemetry><span>Custom Telemetry</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesdeleteall-li><a href=/docs/bestpractices/deleteall/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesdeleteall><span>DeleteAll</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesend-else-pair-li><a href=/docs/bestpractices/end-else-pair/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesend-else-pair><span>end else pair</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticeskeyword-pairs-indentation-li><a href=/docs/bestpractices/keyword-pairs-indentation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticeskeyword-pairs-indentation><span>Keyword Pairs - Indentation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesline-start-keywords-li><a href=/docs/bestpractices/line-start-keywords/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesline-start-keywords><span>Line Start Keywords</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticeslonely-repeat-li><a href=/docs/bestpractices/lonely-repeat/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticeslonely-repeat><span>Lonely Repeat</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesnamed-invocations-li><a href=/docs/bestpractices/named-invocations/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesnamed-invocations><span>Named Invocations</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesone-statement-per-line-li><a href=/docs/bestpractices/one-statement-per-line/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesone-statement-per-line><span>One Statement per Line</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesseparate-if-and-else-li><a href=/docs/bestpractices/separate-if-and-else/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesseparate-if-and-else><span>Seperate if and else</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesspacing-binary-operators-li><a href=/docs/bestpractices/spacing-binary-operators/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesspacing-binary-operators><span>Spacing Binary Operators</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticessubscribercodeunits-li><a href=/docs/bestpractices/subscribercodeunits/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticessubscribercodeunits><span>Subscriber Codeunits</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticessuggested-abbreviations-li><a href=/docs/bestpractices/suggested-abbreviations/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticessuggested-abbreviations><span>Suggested Abbreviations</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesunnecessary-else-li><a href=/docs/bestpractices/unnecessary-else/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesunnecessary-else><span>Unnecessary else</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesunnecessary-truefalse-li><a href=/docs/bestpractices/unnecessary-truefalse/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesunnecessary-truefalse><span>Unnecessary true/false</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesvariable-naming-li><a href=/docs/bestpractices/variable-naming/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesvariable-naming><span>Variable Naming</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesvariables-declarations-order-li><a href=/docs/bestpractices/variables-declarations-order/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesvariables-declarations-order><span>Variables Declarations Order</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsbestpracticesblank-lines-when-not-to-use-li><a href=/docs/bestpractices/blank-lines-when-not-to-use/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsbestpracticesblank-lines-when-not-to-use><span>When not to use Blank Lines</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child" id=m-docsnavpatterns-li><a href=/docs/navpatterns/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns><span>NAV Patterns Archive</span></a><ul class="ul-2 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatterns-li><a href=/docs/navpatterns/patterns/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatterns><span>1. Patterns</span></a><ul class="ul-3 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsactivity-log-li><a href=/docs/navpatterns/patterns/activity-log/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsactivity-log><span>Activity Logs</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsargument-table-li><a href=/docs/navpatterns/patterns/argument-table/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsargument-table><span>Argument Table</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternsblocked-entity-li><a href=/docs/navpatterns/patterns/blocked-entity/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternsblocked-entity><span>Blocked Entity</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsblocked-entitydata-driven-blocked-entity-li><a href=/docs/navpatterns/patterns/blocked-entity/data-driven-blocked-entity/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsblocked-entitydata-driven-blocked-entity><span>Data Driven Blocked Entity</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscached-web-service-calls-li><a href=/docs/navpatterns/patterns/cached-web-service-calls/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscached-web-service-calls><span>Cached Web Server Calls</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsconditional-cascading-update-li><a href=/docs/navpatterns/patterns/conditional-cascading-update/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsconditional-cascading-update><span>Conditional Cascading Update</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscopy-document-li><a href=/docs/navpatterns/patterns/copy-document/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscopy-document><span>Copy Document</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscreate-data-from-templates-li><a href=/docs/navpatterns/patterns/create-data-from-templates/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscreate-data-from-templates><span>Create Data from Templates</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscreate-urls-to-nav-clients-li><a href=/docs/navpatterns/patterns/create-urls-to-nav-clients/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscreate-urls-to-nav-clients><span>Create URLs to NAV Clients</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscreating-custom-charts-li><a href=/docs/navpatterns/patterns/creating-custom-charts/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscreating-custom-charts><span>Creating Custom Charts</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscross-session-events-li><a href=/docs/navpatterns/patterns/cross-session-events/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscross-session-events><span>Cross Session Events</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternscurrently-active-record-li><a href=/docs/navpatterns/patterns/currently-active-record/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternscurrently-active-record><span>Currently Active Record</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsdata-migration-facade-li><a href=/docs/navpatterns/patterns/data-migration-facade/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsdata-migration-facade><span>Data Migration Façade</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsdiscovery-event-li><a href=/docs/navpatterns/patterns/discovery-event/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsdiscovery-event><span>Discovery Event</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsdocument-li><a href=/docs/navpatterns/patterns/document/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsdocument><span>Document</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternseasy-update-of-setup-or-supplementary-information-li><a href=/docs/navpatterns/patterns/easy-update-of-setup-or-supplementary-information/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternseasy-update-of-setup-or-supplementary-information><span>Easy Update Of Setup Or Supplementary Information</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternserror-message-processing-li><a href=/docs/navpatterns/patterns/error-message-processing/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternserror-message-processing><span>Error Message Processing</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsextending-the-role-center-headlines-li><a href=/docs/navpatterns/patterns/extending-the-role-center-headlines/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsextending-the-role-center-headlines><span>Extending the Role Center Headlines</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsfeature-localization-for-data-structures-li><a href=/docs/navpatterns/patterns/feature-localization-for-data-structures/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsfeature-localization-for-data-structures><span>Feature Localization For Data Structures</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternshooks-li><a href=/docs/navpatterns/patterns/hooks/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternshooks><span>Hooks</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsimplementation-of-surrogate-keys-using-autoincrement-pattern-li><a href=/docs/navpatterns/patterns/implementation-of-surrogate-keys-using-autoincrement-pattern/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsimplementation-of-surrogate-keys-using-autoincrement-pattern><span>Surrogate keys using Autoincrement Pattern</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsinstructions-in-the-ui-li><a href=/docs/navpatterns/patterns/instructions-in-the-ui/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsinstructions-in-the-ui><span>Instructions in the UI</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsintegration-of-addresses-li><a href=/docs/navpatterns/patterns/integration-of-addresses/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsintegration-of-addresses><span>Integration of Addresses</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsjournal-error-processing-li><a href=/docs/navpatterns/patterns/journal-error-processing/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsjournal-error-processing><span>Journal Error Processing</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsjournal-template-batch-line-li><a href=/docs/navpatterns/patterns/journal-template-batch-line/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsjournal-template-batch-line><span>Journal Template Batch Line</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsmaster-data-li><a href=/docs/navpatterns/patterns/master-data/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsmaster-data><span>Master Data</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsmulti-file-download-li><a href=/docs/navpatterns/patterns/multi-file-download/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsmulti-file-download><span>Multi-file Download</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsmulti-page-list-li><a href=/docs/navpatterns/patterns/multi-page-list/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsmulti-page-list><span>Multi-Page List</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsmultilanguage-application-data-li><a href=/docs/navpatterns/patterns/multilanguage-application-data/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsmultilanguage-application-data><span>Multilanguage Application Data</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternsnet-exception-handling-in-cal-li><a href=/docs/navpatterns/patterns/net-exception-handling-in-cal/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternsnet-exception-handling-in-cal><span>NET Exception Handling in CAL</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsnet-exception-handling-in-caltryfunction-net-exception-handling-in-cal-li><a href=/docs/navpatterns/patterns/net-exception-handling-in-cal/tryfunction-net-exception-handling-in-cal/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsnet-exception-handling-in-caltryfunction-net-exception-handling-in-cal><span>TryFunction NET Exception Handling in CAL</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsno-series-li><a href=/docs/navpatterns/patterns/no-series/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsno-series><span>No Series</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternsnotifications-li><a href=/docs/navpatterns/patterns/notifications/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternsnotifications><span>Notifications</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsnotificationsin-context-notifications-li><a href=/docs/navpatterns/patterns/notifications/in-context-notifications/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsnotificationsin-context-notifications><span>In-context Notifications</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsnotificationsnotification-lifecycle-management-pattern-li><a href=/docs/navpatterns/patterns/notifications/notification-lifecycle-management-pattern/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsnotificationsnotification-lifecycle-management-pattern><span>Notification Lifecycle Management Pattern</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsobserver-li><a href=/docs/navpatterns/patterns/observer/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsobserver><span>Observer</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsposting-routine-select-behavior-li><a href=/docs/navpatterns/patterns/posting-routine-select-behavior/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsposting-routine-select-behavior><span>Posting Routine - Select Behavior</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsproduct-name-li><a href=/docs/navpatterns/patterns/product-name/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsproduct-name><span>Product Name</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternsqueries-li><a href=/docs/navpatterns/patterns/queries/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternsqueries><span>Queries</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsqueriesselect-distinct-with-queries-li><a href=/docs/navpatterns/patterns/queries/select-distinct-with-queries/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsqueriesselect-distinct-with-queries><span>SELECT DISTINCT with Queries</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsqueriesuse-queries-to-detect-duplicate-records-li><a href=/docs/navpatterns/patterns/queries/use-queries-to-detect-duplicate-records/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsqueriesuse-queries-to-detect-duplicate-records><span>Use Queries to Detect Duplicate Records</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsqueriesuse-queries-to-replace-nested-loops-li><a href=/docs/navpatterns/patterns/queries/use-queries-to-replace-nested-loops/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsqueriesuse-queries-to-replace-nested-loops><span>Use Queries to Replace Nested Loops</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsread-once-initialization-and-validation-li><a href=/docs/navpatterns/patterns/read-once-initialization-and-validation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsread-once-initialization-and-validation><span>Read-once Initialization and Validation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsreleased-entity-li><a href=/docs/navpatterns/patterns/released-entity/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsreleased-entity><span>Released Entity</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsreport-selection-li><a href=/docs/navpatterns/patterns/report-selection/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsreport-selection><span>Report Selection</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternssecurity-li><a href=/docs/navpatterns/patterns/security/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternssecurity><span>Security</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssecurity1-sensitive-data-encapsulation-li><a href=/docs/navpatterns/patterns/security/1-sensitive-data-encapsulation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssecurity1-sensitive-data-encapsulation><span>Sensitive Data Encapsulation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssecurity2-data-encryption-li><a href=/docs/navpatterns/patterns/security/2-data-encryption/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssecurity2-data-encryption><span>Data Encryption</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssecurity3-single-point-of-access-li><a href=/docs/navpatterns/patterns/security/3-single-point-of-access/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssecurity3-single-point-of-access><span>Single Point of Access</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssecurity4-masked-text-li><a href=/docs/navpatterns/patterns/security/4-masked-text/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssecurity4-masked-text><span>Masked Text</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssecurity5-ssl-in-nav-li><a href=/docs/navpatterns/patterns/security/5-ssl-in-nav/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssecurity5-ssl-in-nav><span>SSL in NAV</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssetup-specificity-fallback-li><a href=/docs/navpatterns/patterns/setup-specificity-fallback/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssetup-specificity-fallback><span>Setup Specificity Fallback</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssilent-file-upload-and-download-li><a href=/docs/navpatterns/patterns/silent-file-upload-and-download/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssilent-file-upload-and-download><span>Silent File Upload and Download</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternssingleton-li><a href=/docs/navpatterns/patterns/singleton/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternssingleton><span>Singleton</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssingletonsingleton-codeunit-li><a href=/docs/navpatterns/patterns/singleton/singleton-codeunit/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssingletonsingleton-codeunit><span>Singleton Codeunit</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatternspatternssingletonsingleton-table-li><a href=/docs/navpatterns/patterns/singleton/singleton-table/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatternspatternssingletonsingleton-table><span>Singleton Table</span></a><ul class="ul-5 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssingletonsingleton-tablecue-table-li><a href=/docs/navpatterns/patterns/singleton/singleton-table/cue-table/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssingletonsingleton-tablecue-table><span>Cue Table</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternssingletonsingleton-tablesetup-table-li><a href=/docs/navpatterns/patterns/singleton/singleton-table/setup-table/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternssingletonsingleton-tablesetup-table><span>Setup Table</span></a></li></ul></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsstandard-journal-li><a href=/docs/navpatterns/patterns/standard-journal/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsstandard-journal><span>Standard Journal</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternstemporary-dataset-report-li><a href=/docs/navpatterns/patterns/temporary-dataset-report/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternstemporary-dataset-report><span>Temporary Dataset Report</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternstotals-and-discounts-on-subpages-sales-and-purchases-li><a href=/docs/navpatterns/patterns/totals-and-discounts-on-subpages-sales-and-purchases/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternstotals-and-discounts-on-subpages-sales-and-purchases><span>Totals and Discounts on Subpages Sales and Purchases</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternstransfer-custom-fields-li><a href=/docs/navpatterns/patterns/transfer-custom-fields/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternstransfer-custom-fields><span>Transfer Custom Fields</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatternspatternsvariant-facade-li><a href=/docs/navpatterns/patterns/variant-facade/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatternspatternsvariant-facade><span>Variant Facade</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns2-anti-patterns-li><a href=/docs/navpatterns/2-anti-patterns/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns2-anti-patterns><span>2. Anti-Patterns</span></a><ul class="ul-3 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns2-anti-patternsnav-upgrade-li><a href=/docs/navpatterns/2-anti-patterns/nav-upgrade/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns2-anti-patternsnav-upgrade><span>Nav Upgrade</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns2-anti-patternsreusable-bugs-li><a href=/docs/navpatterns/2-anti-patterns/reusable-bugs/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns2-anti-patternsreusable-bugs><span>Reusable Bugs</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns3-cal-coding-guidelines-li><a href=/docs/navpatterns/3-cal-coding-guidelines/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns3-cal-coding-guidelines><span>3. CAL Coding Guidelines</span></a><ul class="ul-3 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesign-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns3-cal-coding-guidelinesdesign><span>Design</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignby-reference-parameters-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/by-reference-parameters/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignby-reference-parameters><span>By Reference Parameters</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignclass-coupling-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/class-coupling/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignclass-coupling><span>Class Coupling</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesigncyclomatic-complexity-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/cyclomatic-complexity/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesigncyclomatic-complexity><span>Cyclomatic Complexity</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignencapsulate-local-functionality-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/encapsulate-local-functionality/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignencapsulate-local-functionality><span>Encapsulate Local Functionality</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignfindset-findfirst-findlast-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/findset-findfirst-findlast/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignfindset-findfirst-findlast><span>FINDSET FINDFIRST FINDLAST</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesigninitialized-variables-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/initialized-variables/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesigninitialized-variables><span>Initialized Variables</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignmaintainability-index-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/maintainability-index/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignmaintainability-index><span>Maintainability Index</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignparameter-placeholders-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/parameter-placeholders/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignparameter-placeholders><span>Parameter Placeholders</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignstatic-object-invocation-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/static-object-invocation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignstatic-object-invocation><span>Static Object Invocation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignunreachable-code-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/unreachable-code/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignunreachable-code><span>Unreachable Code</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignunused-initialized-variables-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/unused-initialized-variables/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignunused-initialized-variables><span>Unused Initialized Variables</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignunused-variables-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/unused-variables/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignunused-variables><span>Unused Variables</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignvariable-capacity-mismatch-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/variable-capacity-mismatch/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignvariable-capacity-mismatch><span>Variable Capacity Mismatch</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesdesignwith-scope-name-collision-li><a href=/docs/navpatterns/3-cal-coding-guidelines/design/with-scope-name-collision/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesdesignwith-scope-name-collision><span>WITH Scope Name Collision</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesinternally-used-dot-net-types-li><a href=/docs/navpatterns/3-cal-coding-guidelines/internally-used-dot-net-types/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesinternally-used-dot-net-types><span>Internally used DotNet Types</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesinternationalization-li><a href=/docs/navpatterns/3-cal-coding-guidelines/internationalization/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns3-cal-coding-guidelinesinternationalization><span>Internationalization</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesinternationalizationusing-calcdate-li><a href=/docs/navpatterns/3-cal-coding-guidelines/internationalization/using-calcdate/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesinternationalizationusing-calcdate><span>Using Calcdate</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns3-cal-coding-guidelineslocalizability-li><a href=/docs/navpatterns/3-cal-coding-guidelines/localizability/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns3-cal-coding-guidelineslocalizability><span>Localizability</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilitycaptionml-for-system-tables-li><a href=/docs/navpatterns/3-cal-coding-guidelines/localizability/captionml-for-system-tables/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilitycaptionml-for-system-tables><span>CaptionML on System Pages</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityfieldcaption-and-tablecaption-li><a href=/docs/navpatterns/3-cal-coding-guidelines/localizability/fieldcaption-and-tablecaption/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityfieldcaption-and-tablecaption><span>FIELDCAPTION and TABLECAPTION</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityglobal-text-constants-li><a href=/docs/navpatterns/3-cal-coding-guidelines/localizability/global-text-constants/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityglobal-text-constants><span>Global Text Constants</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityuse-text-constants-li><a href=/docs/navpatterns/3-cal-coding-guidelines/localizability/use-text-constants/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityuse-text-constants><span>Use Text Constants</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityusing-optioncaptionml-li><a href=/docs/navpatterns/3-cal-coding-guidelines/localizability/using-optioncaptionml/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelineslocalizabilityusing-optioncaptionml><span>Using OptionCaptionML</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadability-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns3-cal-coding-guidelinesreadability><span>Readability</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitybegin-as-an-afterword-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/begin-as-an-afterword/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitybegin-as-an-afterword><span>Begin as an 'After Word'</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitybegin-end-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/begin-end/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitybegin-end><span>Begin-End - Compound Only</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitybinary-operator-line-start-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/binary-operator-line-start/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitybinary-operator-line-start><span>Binary Operator to Start Line</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityblank-lines-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/blank-lines/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityblank-lines><span>Blank Lines</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycase-actions-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/case-actions/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycase-actions><span>CASE Action</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycolon-usage-in-case-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/colon-usage-in-case/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycolon-usage-in-case><span>Colon usage in CASE</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycomments-curly-brackets-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/comments-curly-brackets/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycomments-curly-brackets><span>Comments inside Curly Brackets</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycomments-spacing-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/comments-spacing/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitycomments-spacing><span>Comment Spacing</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityend-else-pair-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/end-else-pair/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityend-else-pair><span>END ELSE Pair</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityindentation-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/indentation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityindentation><span>Indentation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitykeyword-pairs-indentation-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/keyword-pairs-indentation/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitykeyword-pairs-indentation><span>Keyword Pairs - Indentation</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityline-start-keywords-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/line-start-keywords/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityline-start-keywords><span>Line Start Keywords</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitylonely-repeat-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/lonely-repeat/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitylonely-repeat><span>Lonely Repeat</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitynamed-invocations-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/named-invocations/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitynamed-invocations><span>Named Invocations</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitynested-withs-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/nested-withs/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitynested-withs><span>Nested WITHs</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityone-statement-per-line-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/one-statement-per-line/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityone-statement-per-line><span>One Statement Per Line</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityseparate-if-and-else-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/separate-if-and-else/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityseparate-if-and-else><span>Separate IF and ELSE</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityspacing-binary-operators-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/spacing-binary-operators/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityspacing-binary-operators><span>Spacing Binary Operators</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityspacing-brackets-and-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/spacing-brackets-and/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityspacing-brackets-and><span>Spacing Brackets and ::</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityspacing-unary-operators-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/spacing-unary-operators/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityspacing-unary-operators><span>Spacing Unary Operators</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitysuggested-abbreviations-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/suggested-abbreviations/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitysuggested-abbreviations><span>Suggested Abbreviations</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitytemporary-variable-naming-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/temporary-variable-naming/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitytemporary-variable-naming><span>Temporary Variable Naming</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitytextconst-suffixes-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/textconst-suffixes/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilitytextconst-suffixes><span>TextConst Suffixes</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunary-operator-line-end-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/unary-operator-line-end/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunary-operator-line-end><span>Unary Operator Line End</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-compound-parenthesis-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/unnecessary-compound-parenthesis/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-compound-parenthesis><span>Unnecessary Compound Parenthesis</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-else-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/unnecessary-else/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-else><span>Unnecessary ELSE</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-function-parenthesis-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/unnecessary-function-parenthesis/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-function-parenthesis><span>Unnecessary Function Parenthesis</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-separators-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/unnecessary-separators/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-separators><span>Unnecessary Separators</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-truefalse-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/unnecessary-truefalse/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityunnecessary-truefalse><span>Unnecessary TRUE/FALSE</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityvariable-already-scoped-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/variable-already-scoped/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityvariable-already-scoped><span>Variable Already Scoped</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityvariable-naming-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/variable-naming/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityvariable-naming><span>Variable Naming</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityvariables-declarations-order-li><a href=/docs/navpatterns/3-cal-coding-guidelines/readability/variables-declarations-order/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesreadabilityvariables-declarations-order><span>Variables Declarations Order</span></a></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesux-li><a href=/docs/navpatterns/3-cal-coding-guidelines/ux/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns3-cal-coding-guidelinesux><span>UX</span></a><ul class="ul-4 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesuxactions-images-li><a href=/docs/navpatterns/3-cal-coding-guidelines/ux/actions-images/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesuxactions-images><span>Actions - Images</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesuxconfirm-li><a href=/docs/navpatterns/3-cal-coding-guidelines/ux/confirm/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesuxconfirm><span>CONFIRM</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesuxfielderror-li><a href=/docs/navpatterns/3-cal-coding-guidelines/ux/fielderror/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesuxfielderror><span>FIELDERROR</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns3-cal-coding-guidelinesuxmessage-and-error-li><a href=/docs/navpatterns/3-cal-coding-guidelines/ux/message-and-error/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns3-cal-coding-guidelinesuxmessage-and-error><span>MESSAGE and ERROR</span></a></li></ul></li></ul></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section with-child collapse" id=m-docsnavpatterns4-get-involved-li><a href=/docs/navpatterns/4-get-involved/ class="align-left pl-0 td-sidebar-link td-sidebar-link__section" id=m-docsnavpatterns4-get-involved><span>(OLD) Get Involved</span></a><ul class="ul-3 foldable"><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns4-get-involvedcode-of-conduct-li><a href=/docs/navpatterns/4-get-involved/code-of-conduct/ class="align-left pl-0 td-sidebar-link td-sidebar-link__page" id=m-docsnavpatterns4-get-involvedcode-of-conduct><span>Code of Conduct</span></a></li><li class="td-sidebar-nav__section-title td-sidebar-nav__section without-child collapse" id=m-docsnavpatterns4-get-involvedpatterns-authors-li><a 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<a href=https://github.com/microsoft/alguidelines/issues/new class=td-page-meta--project-issue target=_blank rel=noopener><i class="fas fa-tasks fa-fw"></i> Create project issue</a></div><div class=td-toc><nav id=TableOfContents><ul><li><a href=#abstract>Abstract</a></li><li><a href=#context>Context</a></li><li><a href=#problem>Problem</a></li><li><a href=#description>Description</a><ul><li><a href=#what-is-a-subsystem>What is a subsystem?</a></li><li><a href=#the-pattern>The Pattern</a></li></ul></li><li><a href=#usage>Usage</a></li><li><a href=#benefits>Benefits</a><ul><li><a href=#decoupling>Decoupling</a></li><li><a href=#encapsulation>Encapsulation</a></li><li><a href=#readability>Readability</a></li><li><a href=#testability>Testability</a></li><li><a href=#maintainability>Maintainability</a></li></ul></li><li><a href=#when-not-to-use>When not to use</a></li><li><a href=#snippets>Snippets</a></li><li><a href=#list-of-references>List of references</a></li></ul></nav></div><div class="taxonomy taxonomy-terms-cloud taxo-tags"><h5 class=taxonomy-title>Tag Cloud</h5><ul class=taxonomy-terms><li><a class=taxonomy-term href=https://alguidelines.dev/tags/al/ data-taxonomy-term=al><span class=taxonomy-label>AL</span><span class=taxonomy-count>33</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/api/ data-taxonomy-term=api><span class=taxonomy-label>API</span><span class=taxonomy-count>3</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/c/al/ data-taxonomy-term=c/al><span class=taxonomy-label>C/AL</span><span class=taxonomy-count>136</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/decoupling/ data-taxonomy-term=decoupling><span class=taxonomy-label>Decoupling</span><span class=taxonomy-count>2</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/extendability/ data-taxonomy-term=extendability><span class=taxonomy-label>Extendability</span><span 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class=taxonomy-count>2</span></a></li></ul></div><div class="taxonomy taxonomy-terms-cloud taxo-categories"><h5 class=taxonomy-title>Categories</h5><ul class=taxonomy-terms><li><a class=taxonomy-term href=https://alguidelines.dev/categories/best-practice/ data-taxonomy-term=best-practice><span class=taxonomy-label>Best Practice</span><span class=taxonomy-count>88</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/categories/pattern/ data-taxonomy-term=pattern><span class=taxonomy-label>Pattern</span><span class=taxonomy-count>72</span></a></li></ul></div></aside><main class="col-12 col-md-9 col-xl-8 pl-md-5" role=main><nav aria-label=breadcrumb class=td-breadcrumbs><ol class=breadcrumb><li class=breadcrumb-item><a href=https://alguidelines.dev/docs/>Docs</a></li><li class=breadcrumb-item><a href=https://alguidelines.dev/docs/patterns/>Design Patterns</a></li><li class="breadcrumb-item active" aria-current=page><a href=https://alguidelines.dev/docs/patterns/facade-pattern/>Façade</a></li></ol></nav><div class=td-content><h1>Façade</h1><header class=article-meta><div class="taxonomy taxonomy-terms-article taxo-tags"><h5 class=taxonomy-title>Tags:</h5><ul class=taxonomy-terms><li><a class=taxonomy-term href=https://alguidelines.dev/tags/al/ data-taxonomy-term=al><span class=taxonomy-label>AL</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/decoupling/ data-taxonomy-term=decoupling><span class=taxonomy-label>Decoupling</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/readability/ data-taxonomy-term=readability><span class=taxonomy-label>Readability</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/testability/ data-taxonomy-term=testability><span class=taxonomy-label>Testability</span></a></li><li><a class=taxonomy-term href=https://alguidelines.dev/tags/extendability/ data-taxonomy-term=extendability><span class=taxonomy-label>Extendability</span></a></li></ul></div><div class="taxonomy taxonomy-terms-article taxo-categories"><h5 class=taxonomy-title>Categories:</h5><ul class=taxonomy-terms><li><a class=taxonomy-term href=https://alguidelines.dev/categories/pattern/ data-taxonomy-term=pattern><span class=taxonomy-label>Pattern</span></a></li></ul></div></header><p><em>Created by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides (Gang of Four), Described by Jesper Schulz-Wedde (Microsoft)</em></p><h2 id=abstract>Abstract</h2><p>The intent of this pattern is to provide a unified API to a single or a collection of potentially complex subsystems. If you apply this pattern as a general pattern, you will ensure improved:</p><ul><li>Decoupling</li><li>Encapsulation</li><li>Readability</li><li>Testability</li><li>Maintainability</li></ul><h2 id=context>Context</h2><p>Whenever you want to write an isolated piece of business logic, from now on referred to as subsystem, this pattern should be applicable.</p><h2 id=problem>Problem</h2><p>The facade pattern addresses two main problems:</p><ul><li>Over time as systems grow, they tend to become complex and harder to comprehend. By adding a facade on top of the subsystem, that complexity is hidden, and a clear API is defined.</li><li>Any object or method which is publicly accessible, may not receive breaking changes in future releases without announced deprecation. This complicates maintainability of the system. By adding a facade, you ensure that the subsystem is inaccessible to the outside systems, enabling you to change the implementation details of the subsystem at will.</li></ul><h2 id=description>Description</h2><p>The facade pattern is one of the most commonly used and known patterns, first described the book <a href=https://archive.org/details/designpatternsel00gamm/page/185>Design Patterns: Elements of Reusable Object-Oriented Software</a>. It is classified as a structural pattern. While it originates from the object-oriented world, it for sure also applies to AL. The power of a facade is that it:</p><ul><li>Improves the readability of your subsystem&rsquo;s API, as it acts as an entry point to your subsystem. This also allows for easier documentation of your API, as you can focus it to a few public objects.</li><li>Improves the maintainability of your subsystem, as the internal subsystem can be modified or even completely replaced freely, without risking to break the public API - as long as the facade remains intact.</li><li>Ensures that your code remains loosely coupled and encapsulated, as no other subsystem can take dependencies on your internal implementation details. This also fosters the reusability of your code.</li><li>Suggests what needs most attention in your tests, as you would want to make sure that your subsystem&rsquo;s public API behaves as designed.</li></ul><p>Whenever you develop a functional group or an independent system, which has a clear API, you should add a facade to achieve the above-mentioned benefits.</p><h3 id=what-is-a-subsystem>What is a subsystem?</h3><p>A subsystem is a group of objects, which together provide a set of capabilities. Libraries are excellent examples of such subsystems.
In Business Central, all modules in the System Application are subsystems. Examples are hence every module you will find in the system application, such as:</p><ul><li>Azure Blob Services API</li><li>Barcode</li><li>Cryptography Management</li><li>Encoding</li><li>Image</li><li>RegEx</li><li>&mldr;</li></ul><p>If you can describe a set of capabilities out of context of the rest of the system, chances are you are looking at a subsystem.</p><h3 id=the-pattern>The Pattern</h3><p>This is arguably one of easiest patterns to understand and implement. Loosely speaking, you simply need to smack a wrapper on top of your implementation and hide away your implementation details from the outside world.</p><p><img src=diagram.jpg alt=image></p><p>To achieve this, we are using <a href=https://docs.microsoft.com/bs-cyrl-ba/dynamics365/business-central/dev-itpro/developer/devenv-using-access-modifiers>access modifiers</a>. Let&rsquo;s try to take a look at an example, taken from the system application: <a href=https://github.com/microsoft/ALAppExtensions/tree/main/Modules/System/Image>the Image module</a>. I&rsquo;m using this very simplified example for illustration purposes. Notice, that even the full subsystem at time of writing isn&rsquo;t complex - it merely has a single codeunit containing the implementation details. However, as it is expected that the complexity will increase over time or that the implementation details can change, the subsystem is already equipped with a facade from the beginning.</p><p><em>The Facade</em></p><div class=highlight><pre tabindex=0 style=background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4><code class=language-AL data-lang=AL><span style=display:flex><span><span style=color:#204a87;font-weight:700>codeunit</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#0000cf;font-weight:700>3971</span><span style=color:#f8f8f8;text-decoration:underline> </span>Image<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline></span>{<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>Access<span style=color:#f8f8f8;text-decoration:underline> </span>=<span style=color:#f8f8f8;text-decoration:underline> </span>Public<span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>var</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>ImageImpl<span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>Codeunit</span><span style=color:#f8f8f8;text-decoration:underline> </span>&#34;Image Impl.&#34;<span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// &lt;summary&gt;
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// Creates an image from the specified data stream.
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// &lt;/summary&gt;
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// &lt;param name=&#34;InStream&#34;&gt;A Stream that contains the image data.&lt;/param&gt;
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>procedure</span><span style=color:#f8f8f8;text-decoration:underline> </span>FromStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#ce5c00;font-weight:700>)
</span></span></span><span style=display:flex><span><span style=color:#ce5c00;font-weight:700> </span><span style=color:#204a87;font-weight:700>begin</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>ImageImpl<span style=color:#ce5c00;font-weight:700>.</span>FromStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#ce5c00;font-weight:700>)</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>end</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// &lt;summary&gt;
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// Gets the width in pixels.
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// &lt;/summary&gt;
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#8f5902;font-style:italic>/// &lt;returns&gt;The width in pixels.&lt;/returns&gt;
</span></span></span><span style=display:flex><span><span style=color:#8f5902;font-style:italic></span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>procedure</span><span style=color:#f8f8f8;text-decoration:underline> </span>GetWidth<span style=color:#ce5c00;font-weight:700>()</span><span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>Integer</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>begin</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>exit</span><span style=color:#ce5c00;font-weight:700>(</span>ImageImpl<span style=color:#ce5c00;font-weight:700>.</span>GetWidth<span style=color:#ce5c00;font-weight:700>())</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>end</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline></span>}<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span></code></pre></div><p>The facade codeunit above has some characteristics:</p><ul><li>Access is explicitly set to Public, to underline that this is a facade.</li><li>All methods are public.</li><li>All methods are documented.</li><li>No methods contain any logic. They merely point to implementation details.</li><li>The object naming suggests that it will get referenced from the outside.</li></ul><p>Anyone who wants to access the subsystem, will only have to take a dependency on the facade; the implementation details are not needed nor accessible.</p><p>Anyone who wants to access the subsystem, will only have to relate to this one public facade; the documentation makes it easy-to-understand the subsystem&rsquo;s capabilities.</p><p>Test of the subsystem can be limited to testing the facade - it is strictly speaking the only thing that needs verification, that it functions as designed. It is the contract of the subsystem.</p><p><em>The Subsystem</em></p><div class=highlight><pre tabindex=0 style=background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4><code class=language-AL data-lang=AL><span style=display:flex><span><span style=color:#204a87;font-weight:700>codeunit</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#0000cf;font-weight:700>3970</span><span style=color:#f8f8f8;text-decoration:underline> </span>&#34;Image Impl.&#34;<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline></span>{<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>Access<span style=color:#f8f8f8;text-decoration:underline> </span>=<span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>Internal</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>var</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>TempBlob<span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>Codeunit</span><span style=color:#f8f8f8;text-decoration:underline> </span>&#34;Temp Blob&#34;<span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>procedure</span><span style=color:#f8f8f8;text-decoration:underline> </span>FromStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#ce5c00;font-weight:700>)
</span></span></span><span style=display:flex><span><span style=color:#ce5c00;font-weight:700> </span><span style=color:#204a87;font-weight:700>var</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>OutStream</span><span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>OutStream</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>begin</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>TempBlob<span style=color:#ce5c00;font-weight:700>.</span>CreateOutStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>OutStream</span><span style=color:#ce5c00;font-weight:700>)</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>CopyStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>OutStream</span><span style=color:#000;font-weight:700>,</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#ce5c00;font-weight:700>)</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>end</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>procedure</span><span style=color:#f8f8f8;text-decoration:underline> </span>GetWidth<span style=color:#ce5c00;font-weight:700>()</span><span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>Integer</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>var</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>Image<span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>DotNet</span><span style=color:#f8f8f8;text-decoration:underline> </span>Image<span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#000;font-weight:700>:</span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>begin</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>TempBlob<span style=color:#ce5c00;font-weight:700>.</span>CreateInStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#ce5c00;font-weight:700>)</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span>Image<span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#ce5c00;font-weight:700>:=</span><span style=color:#f8f8f8;text-decoration:underline> </span>Image<span style=color:#ce5c00;font-weight:700>.</span>FromStream<span style=color:#ce5c00;font-weight:700>(</span><span style=color:#204a87;font-weight:700>InStream</span><span style=color:#ce5c00;font-weight:700>)</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>exit</span><span style=color:#ce5c00;font-weight:700>(</span>Image<span style=color:#ce5c00;font-weight:700>.</span>Width<span style=color:#ce5c00;font-weight:700>())</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline> </span><span style=color:#204a87;font-weight:700>end</span><span style=color:#000;font-weight:700>;</span><span style=color:#f8f8f8;text-decoration:underline>
</span></span></span><span style=display:flex><span><span style=color:#f8f8f8;text-decoration:underline></span>}<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span></code></pre></div><p>There are no rules for the subsystem, except that access needs to be <strong>internal</strong>. How you implement, how much you document, how you test, is entirely up to you and not the business of the outside caller. Of course, you should apply all of the best practices and patterns anyway, as you and possibly other developers will have to understand, extend and maintain the subsystem too. But from the view of this pattern, the complexity of the subsystem is irrelevant - just as long as it&rsquo;s not accessible.</p><h2 id=usage>Usage</h2><p>The facade pattern is one of the most prominent patterns in the <a href=https://github.com/microsoft/ALAppExtensions/tree/main/Modules/System>system application</a>. You will find plenty of examples here.</p><h2 id=benefits>Benefits</h2><p>The benefits of this rather simple pattern should be abundantly clear by now. But let&rsquo;s go over them once more, structured by the advantages this patterns brings:</p><h3 id=decoupling>Decoupling</h3><p>As the entire subsystem is inaccessible to outside systems, no dependencies can be taken. Hence this patterns strongly promotes the decoupling of objects.</p><h3 id=encapsulation>Encapsulation</h3><p>The entire purpose of this very pattern is to encapsulate complexity; you hide away the implementation details behind an easy to understand facade.</p><h3 id=readability>Readability</h3><p>If done right, the developer doesn&rsquo;t need to be able to understand the details of the subsystem. Everything relevant to using the subsystem is described in the facade.</p><h3 id=testability>Testability</h3><p>Ensuring the correct behaviour of the subsystem can be done by testing the facade. The facade defines the contract of your subsystem - what does it expose and how should it behave. That contract should be covered with adequate tests, which will ensure that it is upheld, even if you decide to change the implementation of the subsystem.</p><h3 id=maintainability>Maintainability</h3><p>The one thing you may not change freely, is the facade and the test of the facade. It can be extended, but you should not break any existing APIs. But that leaves the entire subsystem to be completely rewritten, if you desire to do so. As no external dependencies can exist, there is no risk of introducing any syntactical breaking changes to the outside world. And as the tests of the public facade remain, there is no risk of introducing semantical breaking changes either - the contract is upheld, as long as your tests pass.</p><h2 id=when-not-to-use>When not to use</h2><p>This is a very applicable pattern, which can be used in most cases. While it may appear to be overkill at the beginning of the design of your subsystem, chances are your subsystem will evolve in complexity over time. The pattern may complicate implementation of extensibility, as you hide away all implementation details and hence also take away the opportunity to extend those, but that does not mean that extensibility cannot be achieved - but it requires more careful designing for extensibility. Extensibility with facades could be a topic of its own, which for now isn&rsquo;t covered by this pattern description. As always, use your common sense when to use and when not to use this pattern.</p><h2 id=snippets>Snippets</h2><p>Given the simplicity of this pattern, there are no snippets available at the moment.</p><h2 id=list-of-references>List of references</h2><p>This is one of the most commonly used and discussed, initially described here:</p><p><a href=https://archive.org/details/designpatternsel00gamm/page/185>Design Patterns: Elements of Reusable Object-Oriented Software</a>. Addison Wesley. pp. 185ff. ISBN 0-201-63361-2.</p><p>It is also a key pattern in the design of our system application modules, which is described here:</p><p><a href=https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/devenv-blueprint>Module Architecture</a></p><div class="text-muted mt-5 pt-3 border-top">Last modified February 24, 2022: <a href=https://github.com/microsoft/alguidelines/commit/fb17dc9640ceef53d1f3b8bbf9e9791ef92fabbc>Removed Discussion Links. Using new Theme solution. (fb17dc96)</a>
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