ReSharper 2020.1 Help

Code Syntax Style: Trailing Commas

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 commma };

Some developers consider the trailing comma redundant, but it has a number of benefints, especially in multi-line declarations:

  • It is easier to add or remove the last item, because it is always another single line. You can also press Control+D to duplicate the last line.

  • Your version control diffs are cleaner when you add a new item in the end of the list.

  • It is easier to create code generators for initializers.

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 removing 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 default profiles Full Cleanup or Reformat & Apply Syntax Style, or create and run a custom profile solely targeted at your specific task as described below.

Apply trailing comma style with custom Code Cleanup profile

  1. Select ReSharper | Options from the main menu or press Alt+R O.

  2. Go to the Code Cleanup settings page: Code Editing | Code Cleanup.

  3. 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.

  4. Click Save 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, see Manage and Share ReSharper Settings.

  5. Select the scope where you want to enforce your preferences:

    • Set 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.

  6. Do one of the following:

    • Press Control+Alt+F 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.

  7. In the Code Cleanup dialog that opens, select the newly created profile.

  8. Click Run. ReSharper will enforce your preferences in the selected scope.

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

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.

  1. Go to the Code Editing | C# | Syntax Style page of ReSharper options (Alt+R O).

  2. In the Trailing comma category, specify whether the trailing comma should be preferred in single-line and/or multi-line declarations.

  3. The Notify with selectors in the right column allow you to set severity levels of code inspections detecting code that differs from your preferences.

  4. Click Save 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, see Manage and Share ReSharper Settings.

Applicability in different languages

This feature is supported in the following languages and technologies:

Language: C#Language: VB.NETLanguage: C++Language: HTMLLanguage: ASP.NETLanguage: RazorLanguage: JavaScriptLanguage: TypeScriptLanguage: CSSLanguage: XMLLanguage: XAMLLanguage: ResxLanguage: Build ScriptsLanguage: ProtobufLanguage: JSON
Last modified: 14 July 2020