JetBrains Rider 2020.3 Help

Code Syntax Style: Default Value Expressions ('default' vs 'default(T)')

When you evaluate a default value of a type with the default value expression, and the type can be inferred, you can use either the default(T) operator or the default expression.
In other words, type specification (T) is optional with default when the type can be inferred.

Depending on the context, the optional type specification can either clutter your code with redundant information or, on the contrary, improve the readability.
Therefore, JetBrains Rider provides two code style preferences for default value expressions:

  • when the type is evident from usage (for example, in parameter declarations or field initializations),

  • when the type is not evident (for example, in method call arguments or return statements).

JetBrains Rider helps you enforce style preferences for default value expressions 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 default value expressions

By default, JetBrains Rider highlights type specifications as redundant and helps removing them:

JetBrains Rider syntax style inspection: Use 'default' literal

If you prefer to have explicit type specifications in your code, you can change the corresponding preferences and JetBrains Rider will help you add missing type specifications:

JetBrains Rider syntax style inspection: Specify type

Another option to enforce your preferences for default value expressions 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.

Apply default value style with custom Code Cleanup profile

  1. Press Ctrl+Alt+S or choose File | Settings (Windows and Linux) or JetBrains Rider | Preferences (macOS) from the menu .

  2. Go to the cleanup profiles settings page: Editor | 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 Apply default value style ('default' vs 'default(T)') checkbox. Optionally, you can enable other code cleanup tasks in this profile.

  4. Click Save in the Settings dialog to apply the modifications and let JetBrains Rider choose where to save them, or save the modifications to a specific settings layer using the Save To list. For more information, see Layer-Based 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. Choose Code | Code Cleanup in the main menu.

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

  8. Click OK. JetBrains Rider will enforce your preferences in the selected scope.

If you want to enforce style preferences for default value expressions 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 . Ctrl+E, F . You can also create a custom cleanup profile that would combine arranging default value expressions with other code style tasks.

Configure preferences for default value expressions

Your default value expressions' 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 Editor | Code Style | C# page of JetBrains Rider settings Ctrl+Alt+S , and then select the Syntax Style tab .

  2. In the Default value category, specify whether the type specification should be preferred when the type is evident/non-evident from usage.

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

  4. Click Save in the Settings dialog to apply the modifications and let JetBrains Rider choose where to save them, or save the modifications to a specific settings layer using the Save To list. For more information, see Layer-Based Settings.

Last modified: 10 December 2020