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337 lines
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<li data-nav-id=/welcome/ title=Welcome class=dd-item><a href=/welcome/><b><i class="fas fa-home"></i> </b>Welcome</a><ul></ul></li>
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<li data-nav-id=/bcpatterns/ title="BC Patterns" class=dd-item><a href=/bcpatterns/><b><i class="fas fa-clone"></i> </b>BC Patterns</a><ul>
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<li data-nav-id=/bcpatterns/facade-pattern/ title="Facade Pattern" class=dd-item><a href=/bcpatterns/facade-pattern/>Facade Pattern</a></li>
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<li data-nav-id=/bcpatterns/generic-method-pattern/ title="Generic Method Pattern" class=dd-item><a href=/bcpatterns/generic-method-pattern/>Generic Method Pattern</a></li></ul></li>
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<li data-nav-id=/bcbestpractices/ title="BC Dev. Best Practices" class=dd-item><a href=/bcbestpractices/><b><i class="fas fa-medal"></i> </b>BC Dev. Best Practices</a><ul>
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<li data-nav-id=/bcbestpractices/readability/ title=Readability class=dd-item><a href=/bcbestpractices/readability/>Readability</a><ul>
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<li data-nav-id=/bcbestpractices/readability/begin-as-an-afterword/ title="begin as an 'After Word'" class=dd-item><a href=/bcbestpractices/readability/begin-as-an-afterword/>begin as an 'After Word'</a></li>
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<li data-nav-id=/bcbestpractices/readability/begin-end/ title="Begin-End - Compound Only" class=dd-item><a href=/bcbestpractices/readability/begin-end/>Begin-End - Compound Only</a></li>
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<li data-nav-id=/bcbestpractices/readability/binary-operator-line-start/ title="Binary Operator to Start Line" class=dd-item><a href=/bcbestpractices/readability/binary-operator-line-start/>Binary Operator to Start Line</a></li>
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<li data-nav-id=/bcbestpractices/readability/comments-spacing/ title="Comment Spacing" class=dd-item><a href=/bcbestpractices/readability/comments-spacing/>Comment Spacing</a></li>
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<li data-nav-id=/bcbestpractices/readability/keyword-pairs-indentation/ title="Keyword Pairs - Indentation" class=dd-item><a href=/bcbestpractices/readability/keyword-pairs-indentation/>Keyword Pairs - Indentation</a></li>
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<li data-nav-id=/bcbestpractices/readability/lonely-repeat/ title="Lonely Repeat" class=dd-item><a href=/bcbestpractices/readability/lonely-repeat/>Lonely Repeat</a></li>
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<li data-nav-id=/bcbestpractices/readability/named-invocations/ title="Named Invocations" class=dd-item><a href=/bcbestpractices/readability/named-invocations/>Named Invocations</a></li>
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<li data-nav-id=/bcbestpractices/readability/one-statement-per-line/ title="One Statement Per Line" class=dd-item><a href=/bcbestpractices/readability/one-statement-per-line/>One Statement Per Line</a></li>
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<li data-nav-id=/bcbestpractices/readability/separate-if-and-else/ title="Separate if and else" class=dd-item><a href=/bcbestpractices/readability/separate-if-and-else/>Separate if and else</a></li>
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<li data-nav-id=/bcbestpractices/readability/spacing-binary-operators/ title="Spacing Binary Operators" class=dd-item><a href=/bcbestpractices/readability/spacing-binary-operators/>Spacing Binary Operators</a></li>
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<li data-nav-id=/bcbestpractices/readability/suggested-abbreviations/ title="Suggested Abbreviations" class=dd-item><a href=/bcbestpractices/readability/suggested-abbreviations/>Suggested Abbreviations</a></li>
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<li data-nav-id=/bcbestpractices/readability/unnecessary-else/ title="Unnecessary 'else'" class=dd-item><a href=/bcbestpractices/readability/unnecessary-else/>Unnecessary 'else'</a></li>
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<li data-nav-id=/bcbestpractices/readability/variable-naming/ title="Variable Naming" class=dd-item><a href=/bcbestpractices/readability/variable-naming/>Variable Naming</a></li>
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<li data-nav-id=/bcbestpractices/readability/variables-declarations-order/ title="Variables Declarations Order" class=dd-item><a href=/bcbestpractices/readability/variables-declarations-order/>Variables Declarations Order</a></li></ul></li></ul></li>
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<li data-nav-id=/navpatterns/ title="NAV Patterns Archive" class="dd-item parent"><a href=/navpatterns/><b><i class="fas fa-save"></i> </b>NAV Patterns Archive</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/ title="1. Patterns" class="dd-item parent"><a href=/navpatterns/1-patterns/>1. Patterns</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/activity-log/ title="Activity Logs" class=dd-item><a href=/navpatterns/1-patterns/activity-log/>Activity Logs</a></li>
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<li data-nav-id=/navpatterns/1-patterns/argument-table/ title="Argument Table" class=dd-item><a href=/navpatterns/1-patterns/argument-table/>Argument Table</a></li>
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<li data-nav-id=/navpatterns/1-patterns/blocked-entity/ title="Blocked Entity" class=dd-item><a href=/navpatterns/1-patterns/blocked-entity/>Blocked Entity</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/blocked-entity/data-driven-blocked-entity/ title="Data Driven Blocked Entity" class=dd-item><a href=/navpatterns/1-patterns/blocked-entity/data-driven-blocked-entity/>Data Driven Blocked Entity</a></li></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/cached-web-service-calls/ title="Cached Web Server Calls" class=dd-item><a href=/navpatterns/1-patterns/cached-web-service-calls/>Cached Web Server Calls</a></li>
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<li data-nav-id=/navpatterns/1-patterns/conditional-cascading-update/ title="Conditional Cascading Update" class=dd-item><a href=/navpatterns/1-patterns/conditional-cascading-update/>Conditional Cascading Update</a></li>
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<li data-nav-id=/navpatterns/1-patterns/copy-document/ title="Copy Document" class=dd-item><a href=/navpatterns/1-patterns/copy-document/>Copy Document</a></li>
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<li data-nav-id=/navpatterns/1-patterns/create-data-from-templates/ title="Create Data from Templates" class=dd-item><a href=/navpatterns/1-patterns/create-data-from-templates/>Create Data from Templates</a></li>
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<li data-nav-id=/navpatterns/1-patterns/create-urls-to-nav-clients/ title="Create URLs to NAV Clients" class=dd-item><a href=/navpatterns/1-patterns/create-urls-to-nav-clients/>Create URLs to NAV Clients</a></li>
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<li data-nav-id=/navpatterns/1-patterns/creating-custom-charts/ title="Creating Custom Charts" class=dd-item><a href=/navpatterns/1-patterns/creating-custom-charts/>Creating Custom Charts</a></li>
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<li data-nav-id=/navpatterns/1-patterns/cross-session-events/ title="Cross Session Events" class=dd-item><a href=/navpatterns/1-patterns/cross-session-events/>Cross Session Events</a></li>
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<li data-nav-id=/navpatterns/1-patterns/currently-active-record/ title="Currently Active Record" class=dd-item><a href=/navpatterns/1-patterns/currently-active-record/>Currently Active Record</a></li>
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<li data-nav-id=/navpatterns/1-patterns/data-migration-facade/ title="Data Migration Façade" class=dd-item><a href=/navpatterns/1-patterns/data-migration-facade/>Data Migration Façade</a></li>
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<li data-nav-id=/navpatterns/1-patterns/discovery-event/ title="Discovery Event" class=dd-item><a href=/navpatterns/1-patterns/discovery-event/>Discovery Event</a></li>
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<li data-nav-id=/navpatterns/1-patterns/document/ title=Document class=dd-item><a href=/navpatterns/1-patterns/document/>Document</a></li>
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<li data-nav-id=/navpatterns/1-patterns/easy-update-of-setup-or-supplementary-information/ title="Easy Update Of Setup Or Supplementary Information" class=dd-item><a href=/navpatterns/1-patterns/easy-update-of-setup-or-supplementary-information/>Easy Update Of Setup Or Supplementary Information</a></li>
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<li data-nav-id=/navpatterns/1-patterns/error-message-processing/ title="Error Message Processing" class=dd-item><a href=/navpatterns/1-patterns/error-message-processing/>Error Message Processing</a></li>
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<li data-nav-id=/navpatterns/1-patterns/extending-the-role-center-headlines/ title="Extending the Role Center Headlines" class=dd-item><a href=/navpatterns/1-patterns/extending-the-role-center-headlines/>Extending the Role Center Headlines</a></li>
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<li data-nav-id=/navpatterns/1-patterns/feature-localization-for-data-structures/ title="Feature Localization For Data Structures" class=dd-item><a href=/navpatterns/1-patterns/feature-localization-for-data-structures/>Feature Localization For Data Structures</a></li>
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<li data-nav-id=/navpatterns/1-patterns/hooks/ title=Hooks class=dd-item><a href=/navpatterns/1-patterns/hooks/>Hooks</a></li>
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<li data-nav-id=/navpatterns/1-patterns/implementation-of-surrogate-keys-using-autoincrement-pattern/ title="Surrogate keys using Autoincrement Pattern" class=dd-item><a href=/navpatterns/1-patterns/implementation-of-surrogate-keys-using-autoincrement-pattern/>Surrogate keys using Autoincrement Pattern</a></li>
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<li data-nav-id=/navpatterns/1-patterns/instructions-in-the-ui/ title="Instructions in the UI" class=dd-item><a href=/navpatterns/1-patterns/instructions-in-the-ui/>Instructions in the UI</a></li>
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<li data-nav-id=/navpatterns/1-patterns/integration-of-addresses/ title="Integration of Addresses" class=dd-item><a href=/navpatterns/1-patterns/integration-of-addresses/>Integration of Addresses</a></li>
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<li data-nav-id=/navpatterns/1-patterns/journal-error-processing/ title="Journal Error Processing" class=dd-item><a href=/navpatterns/1-patterns/journal-error-processing/>Journal Error Processing</a></li>
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<li data-nav-id=/navpatterns/1-patterns/journal-template-batch-line/ title="Journal Template Batch Line" class=dd-item><a href=/navpatterns/1-patterns/journal-template-batch-line/>Journal Template Batch Line</a></li>
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<li data-nav-id=/navpatterns/1-patterns/master-data/ title="Master Data" class=dd-item><a href=/navpatterns/1-patterns/master-data/>Master Data</a></li>
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<li data-nav-id=/navpatterns/1-patterns/multi-file-download/ title="Multi-file Download" class=dd-item><a href=/navpatterns/1-patterns/multi-file-download/>Multi-file Download</a></li>
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<li data-nav-id=/navpatterns/1-patterns/multi-page-list/ title="Multi-Page List" class=dd-item><a href=/navpatterns/1-patterns/multi-page-list/>Multi-Page List</a></li>
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<li data-nav-id=/navpatterns/1-patterns/multilanguage-application-data/ title="Multilanguage Application Data" class=dd-item><a href=/navpatterns/1-patterns/multilanguage-application-data/>Multilanguage Application Data</a></li>
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<li data-nav-id=/navpatterns/1-patterns/net-exception-handling-in-cal/ title="NET Exception Handling in CAL" class=dd-item><a href=/navpatterns/1-patterns/net-exception-handling-in-cal/>NET Exception Handling in CAL</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/net-exception-handling-in-cal/tryfunction-net-exception-handling-in-cal/ title="TryFunction NET Exception Handling in CAL" class=dd-item><a href=/navpatterns/1-patterns/net-exception-handling-in-cal/tryfunction-net-exception-handling-in-cal/>TryFunction NET Exception Handling in CAL</a></li></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/no-series/ title="No Series" class=dd-item><a href=/navpatterns/1-patterns/no-series/>No Series</a></li>
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<li data-nav-id=/navpatterns/1-patterns/notifications/ title=Notifications class=dd-item><a href=/navpatterns/1-patterns/notifications/>Notifications</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/notifications/in-context-notifications/ title="In-context Notifications" class=dd-item><a href=/navpatterns/1-patterns/notifications/in-context-notifications/>In-context Notifications</a></li>
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<li data-nav-id=/navpatterns/1-patterns/notifications/notification-lifecycle-management-pattern/ title="Notification Lifecycle Management Pattern" class=dd-item><a href=/navpatterns/1-patterns/notifications/notification-lifecycle-management-pattern/>Notification Lifecycle Management Pattern</a></li></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/observer/ title=Observer class=dd-item><a href=/navpatterns/1-patterns/observer/>Observer</a></li>
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<li data-nav-id=/navpatterns/1-patterns/posting-routine-select-behavior/ title="Posting Routine - Select Behavior" class=dd-item><a href=/navpatterns/1-patterns/posting-routine-select-behavior/>Posting Routine - Select Behavior</a></li>
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<li data-nav-id=/navpatterns/1-patterns/product-name/ title="Product Name" class=dd-item><a href=/navpatterns/1-patterns/product-name/>Product Name</a></li>
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<li data-nav-id=/navpatterns/1-patterns/queries/ title=Queries class=dd-item><a href=/navpatterns/1-patterns/queries/>Queries</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/queries/select-distinct-with-queries/ title="SELECT DISTINCT with Queries" class=dd-item><a href=/navpatterns/1-patterns/queries/select-distinct-with-queries/>SELECT DISTINCT with Queries</a></li>
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<li data-nav-id=/navpatterns/1-patterns/queries/use-queries-to-detect-duplicate-records/ title="Use Queries to Detect Duplicate Records" class=dd-item><a href=/navpatterns/1-patterns/queries/use-queries-to-detect-duplicate-records/>Use Queries to Detect Duplicate Records</a></li>
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<li data-nav-id=/navpatterns/1-patterns/queries/use-queries-to-replace-nested-loops/ title="Use Queries to Replace Nested Loops" class=dd-item><a href=/navpatterns/1-patterns/queries/use-queries-to-replace-nested-loops/>Use Queries to Replace Nested Loops</a></li></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/read-once-initialization-and-validation/ title="Read-once Initialization and Validation" class=dd-item><a href=/navpatterns/1-patterns/read-once-initialization-and-validation/>Read-once Initialization and Validation</a></li>
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<li data-nav-id=/navpatterns/1-patterns/released-entity/ title="Released Entity" class=dd-item><a href=/navpatterns/1-patterns/released-entity/>Released Entity</a></li>
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<li data-nav-id=/navpatterns/1-patterns/report-selection/ title="Report Selection" class=dd-item><a href=/navpatterns/1-patterns/report-selection/>Report Selection</a></li>
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<li data-nav-id=/navpatterns/1-patterns/security/ title=Security class=dd-item><a href=/navpatterns/1-patterns/security/>Security</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/security/1-sensitive-data-encapsulation/ title="Sensitive Data Encapsulation" class=dd-item><a href=/navpatterns/1-patterns/security/1-sensitive-data-encapsulation/>Sensitive Data Encapsulation</a></li>
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<li data-nav-id=/navpatterns/1-patterns/security/2-data-encryption/ title="Data Encryption" class=dd-item><a href=/navpatterns/1-patterns/security/2-data-encryption/>Data Encryption</a></li>
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<li data-nav-id=/navpatterns/1-patterns/security/3-single-point-of-access/ title="Single Point of Access" class=dd-item><a href=/navpatterns/1-patterns/security/3-single-point-of-access/>Single Point of Access</a></li>
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<li data-nav-id=/navpatterns/1-patterns/security/4-masked-text/ title="Masked Text" class=dd-item><a href=/navpatterns/1-patterns/security/4-masked-text/>Masked Text</a></li>
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<li data-nav-id=/navpatterns/1-patterns/security/5-ssl-in-nav/ title="SSL in NAV" class=dd-item><a href=/navpatterns/1-patterns/security/5-ssl-in-nav/>SSL in NAV</a></li></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/setup-specificity-fallback/ title="Setup Specificity Fallback" class=dd-item><a href=/navpatterns/1-patterns/setup-specificity-fallback/>Setup Specificity Fallback</a></li>
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<li data-nav-id=/navpatterns/1-patterns/silent-file-upload-and-download/ title="Silent File Upload and Download" class=dd-item><a href=/navpatterns/1-patterns/silent-file-upload-and-download/>Silent File Upload and Download</a></li>
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<li data-nav-id=/navpatterns/1-patterns/singleton/ title=Singleton class="dd-item parent"><a href=/navpatterns/1-patterns/singleton/>Singleton</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-codeunit/ title="Singleton Codeunit" class="dd-item active"><a href=/navpatterns/1-patterns/singleton/singleton-codeunit/>Singleton Codeunit</a></li>
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<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-table/ title="Singleton Table" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-table/>Singleton Table</a><ul>
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<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-table/cue-table/ title="Cue Table" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-table/cue-table/>Cue Table</a></li>
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<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-table/setup-table/ title="Setup Table" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-table/setup-table/>Setup Table</a></li></ul></li></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/standard-journal/ title="Standard Journal" class=dd-item><a href=/navpatterns/1-patterns/standard-journal/>Standard Journal</a></li>
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<li data-nav-id=/navpatterns/1-patterns/temporary-dataset-report/ title="Temporary Dataset Report" class=dd-item><a href=/navpatterns/1-patterns/temporary-dataset-report/>Temporary Dataset Report</a></li>
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<li data-nav-id=/navpatterns/1-patterns/totals-and-discounts-on-subpages-sales-and-purchases/ title="Totals and Discounts on Subpages Sales and Purchases" class=dd-item><a href=/navpatterns/1-patterns/totals-and-discounts-on-subpages-sales-and-purchases/>Totals and Discounts on Subpages Sales and Purchases</a></li>
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<li data-nav-id=/navpatterns/1-patterns/transfer-custom-fields/ title="Transfer Custom Fields" class=dd-item><a href=/navpatterns/1-patterns/transfer-custom-fields/>Transfer Custom Fields</a></li>
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<li data-nav-id=/navpatterns/1-patterns/variant-facade/ title="Variant Facade" class=dd-item><a href=/navpatterns/1-patterns/variant-facade/>Variant Facade</a></li></ul></li>
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<li data-nav-id=/navpatterns/2-anti-patterns/ title="2. Anti-Patterns" class=dd-item><a href=/navpatterns/2-anti-patterns/>2. Anti-Patterns</a><ul>
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<li data-nav-id=/navpatterns/2-anti-patterns/nav-upgrade/ title="Nav Upgrade" class=dd-item><a href=/navpatterns/2-anti-patterns/nav-upgrade/>Nav Upgrade</a></li>
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<li data-nav-id=/navpatterns/2-anti-patterns/reusable-bugs/ title="Reusable Bugs" class=dd-item><a href=/navpatterns/2-anti-patterns/reusable-bugs/>Reusable Bugs</a></li></ul></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/ title="3. CAL Coding Guidelines" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/>3. CAL Coding Guidelines</a><ul>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/ title=Design class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/>Design</a><ul>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/by-reference-parameters/ title="By Reference Parameters" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/by-reference-parameters/>By Reference Parameters</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/class-coupling/ title="Class Coupling" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/class-coupling/>Class Coupling</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/cyclomatic-complexity/ title="Cyclomatic Complexity" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/cyclomatic-complexity/>Cyclomatic Complexity</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/encapsulate-local-functionality/ title="Encapsulate Local Functionality" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/encapsulate-local-functionality/>Encapsulate Local Functionality</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/initialized-variables/ title="Initialized Variables" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/initialized-variables/>Initialized Variables</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/maintainability-index/ title="Maintainability Index" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/maintainability-index/>Maintainability Index</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/parameter-placeholders/ title="Parameter Placeholders" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/parameter-placeholders/>Parameter Placeholders</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/static-object-invocation/ title="Static Object Invocation" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/static-object-invocation/>Static Object Invocation</a></li>
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/unreachable-code/ title="Unreachable Code" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/unreachable-code/>Unreachable Code</a></li>
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|
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/unused-initialized-variables/ title="Unused Initialized Variables" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/unused-initialized-variables/>Unused Initialized Variables</a></li>
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|
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|
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|
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/with-scope-name-collision/ title="WITH Scope Name Collision" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/with-scope-name-collision/>WITH Scope Name Collision</a></li></ul></li>
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|
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/internally-used-dot-net-types/ title="Internally used DotNet Types" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/internally-used-dot-net-types/>Internally used DotNet Types</a></li>
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|
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|
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<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/begin-end/ title="Begin-End - Compound Only" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/begin-end/>Begin-End - Compound Only</a></li>
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<h1>Singleton Codeunit</h1>
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<p><em>By Bogdana Botez at Microsoft Development Center Copenhagen</em></p>
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<p><a href=Singleton-Codeunit.png><img src=Singleton-Codeunit.png alt=" "></a></p>
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<p><strong>Problem</strong>: In some situations, global state needs to be preserved at runtime throughout a session.</p>
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<p>There are functionality areas in NAV where centralized application management code is needed, like for example managing permissions, notifications, the debugger etc. State needs to be preserved across calls to the management codeunit.</p>
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<p>For example:</p>
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<ul>
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<li>The debugger needs to remember the session which is being debugged</li>
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<li>The permission manager has a testability function, where it can be set to emulate that it’s running as a SaaS (Software As A Service – the cloud) platform, even when the tests run in a “on-premise” local lab.</li>
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</ul>
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<p>Take for example the following test of Azure ML (Azure Machine Learning) integration with NAV.</p>
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<p>Context: Azure Machine Learning services are paid. However, Dynamics NAV includes a monthly pre-paid quota of Azure ML, which can be used for free by the users. There is an upper limit to this quota, and when it is reached, Azure ML services are turned off until the next month starts and a new quota becomes available for consumption.</p>
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<p>The test below checks that, when the monthly quota is exceeded, then the function IsAzureMLLimitReached returns TRUE.</p>
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<pre><code>\[Test\]
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PROCEDURE AzureMLProcessingTimeExceedsLimit@11();
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VAR
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AzureMachineLearningUsage@1004 : Record 2002;
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ProcessingTime@1000 : Decimal;
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BEGIN
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// \[SCENARIO\] Azure Machine Learning Processing time exceeds AzureML limit
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// \[GIVEN\] AzureMachineLearningUsage \> 0
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Initialize; // calls PermissionManager.SetTestabilitySoftwareAsAService(TRUE);
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ProcessingTime := LibraryRandom.RandDec(1000,2);
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AzureMachineLearningUsage.IncrementTotalProcessingTime(ProcessingTime);
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// \[WHEN\] When IsAzureMLLimitReached is invoked with Limit more than Processing time
|
|
// \[THEN\] HasAzureLimitReached returns TRUE
|
|
Assert.IsTrue(AzureMachineLearningUsage.IsAzureMLLimitReached(ProcessingTime - 1),
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|
'HasAzureLimitReached returns wrong value when Processing time exceeds Limit.');
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PermissionManager.SetTestabilitySoftwareAsAService(FALSE);
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END;
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</code></pre>
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<p>The figure below explains what happens when the Permission Manager is not a singleton. When it is invoked from different places (first from the test, second from the production code), then different instances of the Permission Manager will fire up and answer. In detail:</p>
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<ol>
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<li>The test calls Initialize which sets SaaS=TRUE in codeunit Permission Manager</li>
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|
<li>The test calls into production code to validate it works as expected. It calls AzureMachineLearningUsage codeunit to find out if the monthly quota has been reached. The function IsAzureMLLimitReached in AzureMachineLearningUsage codeunit is designed only for SaaS. If the code doesn’t run in SaaS, then it always returns FALSE.</li>
|
|
<li>Therefore, a call to PermissionManager is made, to find out if the environment is SaaS.</li>
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<li>However, a different instance of Permission Manager is reached – and instance where SaaS was never set to TRUE. This is a mistake – the test intended to simulate SaaS, but the state it set in the beginning is not reachable from production code.</li>
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<li>The production code will assess (wrongly) that it’s not running SaaS, and say that the Azure ML limit has not been reached (incorrect – and the test fails).</li>
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</ol>
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<p><a href=Singleton-Codeunit-_2D00_-example-_2D00_-bad.PNG><img src=Singleton-Codeunit-_2D00_-example-_2D00_-bad.PNG alt=" "></a></p>
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<hr>
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<p><strong>Solution:</strong> restrict the number of instantiations of a codeunit to only one, by setting the codeunit property <strong>SingleInstance</strong> to <strong>Yes</strong>.</p>
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<p>Returning to the previous example, let’s analyze the case when the codeunit Permission Manager is a singleton codeunit:</p>
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<p><a href=2313.Singleton-Codeunit-_2D00_-CSIDE-SingleInstance-property.PNG><img src=2313.Singleton-Codeunit-_2D00_-CSIDE-SingleInstance-property.PNG alt=" "></a></p>
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<p>When the codeunit Permission Manager is a singleton, then no matter from where it is invoked, the same instance will be reached. Therefore, the status set by the test (SaaS = TRUE) will be reachable from the production code, and the test will pass, as seen in the figure below.</p>
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<p>**<a href=Singleton-Codeunit-_2D00_-example-_2D00_-good.PNG><img src=Singleton-Codeunit-_2D00_-example-_2D00_-good.PNG alt=" "></a><br>
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**</p>
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<p><strong>Consequences</strong></p>
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<p>1. Use Singleton Codeunit with care and only when there is no other solution. Preserving a global state could often enough be more harmful than useful. One risk is that tests might fail apparently non-deterministically.</p>
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<p>For example, a problem we have met in the development team for Madeira release, was that the singleton codeunit function PermissionManager.SetSoftwareAsAService(TRUE) is often used to emulate and test SaaS conditions. However, if a test ‘forgets’ to reset the state to default (FALSE), then another codeunit which is not supposed to emulate SaaS, will suddenly run as SaaS and will fail. Even if the test has code that resets the state to FALSE, this code might never be reached because of an earlier failure or other error in the test which would stop execution.</p>
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<p>2. The singleton codeunit is only “alive” for the current session. If the user logs out, the old session is closed and the singleton cleared out so any values stored in the old session’s singleton will be lost when the session was closed. When the user logs in again, a new session (with a new fresh instance of the singleton) will be created.</p>
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<p><strong>NAV Usages</strong></p>
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<p>Most of the usages in NAV refer to the so-called “management codeunits”. The management codeunits are needed to run, in a centralized way, various modular parts of the application (features), like the CRM integration, Permissions, Workflows etc. Some of the <strong>Singleton Codeunits</strong> in NAV are listed below:</p>
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<ul>
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<li>Codeunit 423 Change Log Management</li>
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<li>Codeunit 1503 Workflow Record Management</li>
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<li>Codeunit 1511 Notification Lifecycle Mgt.</li>
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<li>Codeunit 1629 Office Attachment Manager</li>
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<li>Codeunit 1632 Office Error Engine</li>
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<li>Codeunit 5150 Integration Management</li>
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<li>Codeunit 9002 Permission Manager</li>
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<li>Etc.</li>
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</ul>
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<p><strong>Note:</strong> while the object-oriented <strong>Singleton</strong> pattern can restrict the number of instantiations of the singleton to an integer n > 0, in Dynamics NAV the <strong>Singleton Codeunit</strong> can only have n=1.</p>
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