bcquality/microsoft/knowledge/performance/use-textbuilder-for-string-concatenation-in-loops.md

bc-version	domain	keywords	technologies	countries	application-area
all	performance	textbuilder string-concatenation loop append immutable-text	al	w1	all

Use AL TextBuilder for repeated text mutation

Description

AL TextBuilder is a reference type intended for modifying text without creating a new Text value for each change. Microsoft documents it as the performance-oriented AL primitive for concatenating many strings, including loop-built output. Append and AppendLine build the value, and ToText returns the completed text.

Best Practice

When a loop repeatedly appends fragments to one result, use a TextBuilder local and convert once after the loop. Keep ordinary Text expressions for a fixed, small number of fragments; this rule is about repeated mutation, not every concatenation.

Anti Pattern

Building an unbounded export or message with Result += Fragment on every iteration when AL's TextBuilder directly represents the operation.