Best practices for AL 05/16/2025 This page defines some of the best practices to follow when writing AL code for Dynamics 365 Business Central. These best practices are additive to rules and guidelines that are caught during compilation of AL code. We recommend following these best practices when developing extensions in AL to ensure consistency and discoverability on file, object, and method naming, as well as better readability of written code.
Tip
Check out the great work that is going on at https://alguidelines.dev/. New design patterns and best practices are being established, so join the discussions, and contribute through GitHub.
Extension structure An extension is fully contained in a single folder. This folder often contains multiple files, such as app.json and launch.json files, perhaps an image file representing the extension's logo, various folders for source; \src, other resources; \res, and a test folder; \test folder. The extension doesn't need to follow a flat structure, which means that, depending on the number of application files, extra folders can be used in the "src" or "test" folders to group objects based on their functionality, which can help make maintaining a large AL project easier.
File naming Each file name should contain the object name (using only characters A–Z, a–z, and 0–9), the object type, and the .al file extension. In your extension, the name of each new application object (table, page, codeunit), can contain a prefix or suffix.
The CodeCop analyzer suggests that the object name is part of the file name, which is encouraged as a best practice. Adding any affixes to the file names is voluntary.
Note
If you're submitting an app to AppSource, you must follow the guidance in the Technical validation checklist.
File naming notation Follow the syntax for file naming as shown in the table:
Expand table Full objects Extensions ..al .Ext.al ..al .Ext.al ..al .Ext.al Type map Use the listed abbreviations for each type of object in the file naming:
Expand table Object Abbreviation Page Page Page Extension PageExt Page Customization PageCust Codeunit Codeunit Table Table Table Extension TableExt XML Port Xmlport Report Report Request Page RequestPage Query Query Enum Enum Enum Extension EnumExt Control Add-ins ControlAddin Dotnet Dotnet Profile Profile Interface Interface Permission Set PermissionSet Permission Set Extension PermissionSetExt File naming examples For the listed objects in the table, these examples show how to name the files.
Expand table Object name File name codeunit 70000000 MyPrefixSalesperson MyPrefixSalesperson.Codeunit.al page 70000000 MyPrefixSalesperson MyPrefixSalesperson.Page.al pageextension 70000000 MyPrefixSalesperson extends "Customer Card" MyPrefixSalesperson.PageExt.al Examples of object naming Table AL
Copy table 70000000 MyPrefixSalesperson Page AL
Copy page 70000000 MyPrefixSalesperson Action AL
Copy actions { addafter(ApprovalEntries) { action(MyPrefixVacation) Codeunit AL
Copy codeunit 70000000 MyPrefixSalesperson Copilot and action names Trailing whitespaces are allowed in action names, meaning that you don't get a compiler error. For example these names are accepted:
AL
Copy group("CopilotActionGroup ") { action("Suggest Sales Lines ") { // Code that generates sales lines suggestions } } However, these trailing whitespaces are trimmed internally and aren't recognized by Copilot. To ensure that Copilot works correctly with your feature, you must avoid trailing spaces in action names. Instead, write the code like this:
AL
Copy group("CopilotActionGroup") { action("Suggest Sales Lines") { // Code that generates sales lines suggestions } } Formatting We recommend keeping your AL code properly formatted as follows:
Use all lowercase letters for reserved language keywords. Built-in methods and types aren't included in this rule because they're written using Pascal case. Use four spaces for indentation. Curly brackets should always start on a new line. If there's only one property, it can be placed on a single line. The following example illustrates these formatting rules.
AL
Copy page 123 PageName { actions { area(Processing) { action(ActionName) { trigger OnAction() begin end; } } }
var
TempCustomer: Record Customer temporary;
[EventSubscriber(ObjectType::Page, Page::"Item Card", 'OnAfterGetCurrRecordEvent', '', false, false)]
local procedure OnOpenItemCard(var rec: Record Item)
var
OnRecord: Option " ", Item, Contact;
begin
EnablePictureAnalyzerNotification(rec."No.", OnRecord::Item);
end;
}
The AL Language extension for Microsoft Dynamics 365 Business Central offers users the option to automatically format their source code. Learn more in AL Formatter.
Line length In general, there's no restriction on line length, but lengthy lines can make the code unreadable. We recommend that you keep your code easily scannable and readable.
Object naming Object names should be prefixed, starting with the feature or group name, followed by the logical name, as illustrated in the following examples:
Intrastat extension validation codeunit for Denmark codeunit 123 "IntrastatDK Validation" Note
The "MS - " prefix isn't required.
File structure Inside an .al code file, the structure for all objects must follow the sequence:
Properties Object-specific constructs such as Table fields Page layout Actions Triggers Global variables Labels Global variables Methods Referencing In AL, objects are referenced by their object name, not by their ID.
Example AL
Copy Page.RunModal(Page::"Customer Card", ...)
var Customer: Record Customer; Variable and field naming For variables they must:
Be named using PascalCase Have the Temp prefix if they're temporary variables Include the object name in the name (for objects) Furthermore:
Field and variable names shouldn't include wildcard symbols, such as % and &. This might break features such as export using Excel or RapidStart. Name fields using A–Z, a–z, and 0–9 and use Caption and xliff files to display the field appropriately. For more information, see Working with translation files. Using English as the language for naming improves the ability to troubleshoot issues that may arise. Example AL
Copy TempCustomer: Record Customer temporary; Vendor: Record Vendor; Method declaration To declare a method, follow these guidelines:
Include a space after a semicolon when declaring multiple arguments. Semicolons can be used at the end of the signature/method header. If you use a snippet, the semicolons aren't automatically added. Methods should be named using PascalCase, like variables. However, this isn't a mandatory rule. There must be a blank line between method declarations. If you format your code using the AL Formatter tool, the autoformatter sets the blank line between procedures. Example AL
Copy local procedure MyProcedure(Customer: Record Customer; Int: Integer) begin end;
// Blank line between methods
local procedure MyProcedure2(Customer: Record Customer; Int: Integer) begin end;
Calling methods When calling a method, include one space after each command if you're passing multiple parameters. Parentheses must be specified when you're making a method call or system call such as: Init(), Modify(), Insert(), etc.
Example AL
Copy MyProcedure(); MyProcedure(1); MyProcedure(1, 2); Type definition (colon) When you declare a variable or a parameter, the name of that variable or parameter must be immediately followed by a colon, then a single space, and then the type of the variable/parameter as illustrated in the example.
AL
Copy var Number: Integer;
local procedure MyProcedure(a: Integer; b: Integer): Integer Related information Checklist for submitting your app Rules and guidelines for AL code Using the code analysis tool
Additional resources Documentation
Rules and guidelines for AL code - Business Central
Describing the steps you must go through to successfully submit your Dynamics 365 Business Central app to AppSource.
Publishing and Installing an Extension - Business Central
Description of the process of publishing and installing an extension.
Prefix and suffix for naming in extensions - Business Central
Use a prefix or suffix for names in your extension. This rule applies to all objects, including tables, pages, and codeunits. This topic explains the benefits and guidelines for using a prefix or suffix."
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