Code Syntax Style: Trailing Commas

Last modified: 20 November 2023

When multiple items are separated by the comma (object, array, and collection initializers, as well as enums and switch expressions) , C# allows you to have the trailing comma after the last item.

var list = new List<string>
{
    "one",
    "two"
};

var list = new List<string>
{
    "one",
    "two", // trailing comma
};

ReSharper helps you arrange trailing commas in the existing code and takes your preferences into account when it produces new code with code completion and code generation features, applies code templates and performs refactorings.

Enforce preferences for trailing commas

By default, ReSharper highlights trailing commas as redundant and helps remove them:

ReSharper syntax style inspection: Remove trailing comma

If you prefer trailing commas in your code, you can change the corresponding preference and ReSharper will help you add missing trailing commas:

ReSharper syntax style inspection: Add trailing comma

Another option to enforce your preferences for trailing commas in a bulk mode is code cleanup. You can either run code cleanup with one of the built-in profiles Full Cleanup or Reformat & Apply Syntax Style, or create and run a custom profile solely targeted at your specific task as described below.

note
Preferences for trailing commas are not applied to generated code. By default, ReSharper provides the list of file masks and regions for generated code typically produced by Visual Studio (for example, Windows Form Designer-generated code). If necessary, you can edit the list of generated items on the Code Inspection | Generated Code page of ReSharper options ( Alt+R, O ).

Apply trailing comma style with custom Code Cleanup profile

Select ReSharper | Options from the main menu or press Alt+R O.
Go to the cleanup profiles settings page: Code Editing | Code Cleanup | Profiles.
Create a new profile as described in the Create a new custom cleanup profile section. In the Selected profile settings section for the new profile, tick the Arrange trailing commas checkbox. Optionally, you can enable other code cleanup tasks in this profile.
Click Save in the Options dialog to apply the modifications and let ReSharper choose where to save them, or save the modifications to a specific settings layer using the Save To list. For more information, refer to manage and share resharper settings.
Select the scope where you want to enforce your preferences:
- Place the caret anywhere in the file to enforce your preferences to the file.
- Select one or more items in the Solution Explorer to enforce your preferences in the files under these nodes and their child items.
Do one of the following:
- Press Ctrl0E,0C or choose ReSharper | Edit | Cleanup Code… from the main menu .
- Right-click anywhere in the text editor or right-click the selection and choose Cleanup Code in the context menu.
In the Code Cleanup dialog that opens, select the newly created profile .
Click Run. ReSharper will enforce your preferences in the selected scope.

If you want to arrange trailing commas without opening the Code Cleanup dialog to choose a profile, you can bind the created profile to the silent cleanup and run it by pressing Ctrl0E,0F. You can also create a custom cleanup profile that would combine arranging trailing commas with other code style tasks.

To apply preferences for trailing commas together with all other formatting and syntax style rules to the selected code block, AltEnter and choose Reformat and cleanup | Reformat & apply syntax style.

You can arrange trailing commas every time you save changes in a file to make sure that your edits always comply with your code style.

Automatically arrange trailing commas on saving changes

Select ReSharper | Options from the main menu or press Alt+R O.
Go to the cleanup profiles settings page: Code Editing | Code Cleanup | Profiles.
Select your custom Code Cleanup profile and click Set as default (the default profile is also used for silent cleanup).
Go to the Code Editing | Code Cleanup | General options page and select Automatically run cleanup when saving a file.
Optionally, you can restrict automatic cleanup to specific files by a file mask. You can also select Only changed parts of file to make sure that cleanup is applied to the code affected by your changes, and the rest of the code in the file is not modified.
Click Save in the dialog to apply the modifications and let ReSharper choose where to save them, or save the modifications to a specific settings layer using the Save To list. For more information, refer to manage and share resharper settings.
The next time you finish editing and save the file (Ctrl+S) or all files (Ctrl+Shift+S), ReSharper will clean up the affected files using the selected profile. If the default cleanup profile is not selected, ReSharper will prompt you choose one of the profiles.

Configure preferences for trailing commas

Your trailing comma preferences are saved using the mechanism of layer-based settings. Among other things, this mechanism allows you to maintain different preferences for different solutions as well as to keep these preferences under a VCS and automatically share them with your team members.

Go to the Code Editing | C# | Syntax Style page of ReSharper options ( Alt+R, O ).
In the Trailing comma category, specify whether the trailing comma should be preferred in single-line and/or multi-line declarations.
The Notify with selectors in the right column allow you to set severity levels of code inspections detecting code that differs from your preferences.
Click Save in the Options dialog to apply the modifications and let ReSharper choose where to save them, or save the modifications to a specific settings layer using the Save To list. For more information, refer to manage and share resharper settings.