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  1. Code style and cleanup
  2. Syntax styles
  3. Null checking pattern

Code Syntax Style: Null checking pattern

Last modified: 31 March 2023

When checking an expression for null with the type-testing 'is' operator, you can choose between two null-checking patterns:

  • Use the 'not null' pattern that makes the expression more readable.

  • Use the object pattern syntax `{ }` that makes the expression more flexible, allowing you to declare a local variable after it.

'not null' pattern

public static void Test(object? obj)
{
  if (obj is not null)
    Console.WriteLine("not null");
}

'{}' pattern

public static void Test(object? obj)
{
  if (obj is { })
    Console.WriteLine("not null");
}

JetBrains Rider helps you enforce style preferences for null-checking patterns 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 null-checking patterns

By default, JetBrains Rider highlights object pattern syntax { } in null-checking expressions and suggests replace them with the not null pattern:

JetBrains Rider syntax style inspection: Use 'not null' pattern

If you prefer to use the { } pattern, you can change the corresponding preferences and JetBrains Rider will help you replace not null patterns accordingly:

JetBrains Rider syntax style inspection: Use '{ }' pattern

Another option to enforce your preferences for null-checking patterns 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 null-checking patterns are not applied to generated code. By default, JetBrains Rider 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 Editor | Inspection Settings | Generated Code page of JetBrains Rider settings Ctrl+Alt+S.

Apply null-checking pattern 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 Arrange null checking pattern style 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. Press Ctrl+E, C or choose Code | Reformat and Cleanup… from the main menu .

  7. In the Reformat and Cleanup Code dialog that opens, select the newly created profile and choose another scope if needed. .

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

If you want to enforce style preferences for null-checking patterns without opening the Reformat and Cleanup Code 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 null-checking pattern style with other code style tasks.

To apply null-checking pattern style together with all other formatting and syntax style rules to the selected code block, Alt+Enter and choose Reformat and cleanup | Reformat & apply syntax style.

You can enforce style preferences for null-checking patterns in code that you have recently modified and are going to commit to Git. JetBrains Rider will run the selected cleanup profile before committing.

Clean up code before committing it to Git

  1. Press N/A or select Git | Commit from the main menu.

  2. In the Commit tool window, click Show Commit Options and in the Before Commit area, select the Cleanup with... checkbox.

  3. Click Choose profile and choose your custom Code Cleanup profile.

  4. Click Commit or Commit and Push. JetBrains Rider will run code cleanup on the ranges staged for the commit, and then commit the changes.

You can enforce style preferences for null-checking patterns every time you save changes in a file to make sure that your edits always comply with your code style. Note that this will only happen when you save changes explicitly with Ctrl+S or Ctrl+Shift+S and will not be triggered by auto-saving. However, all auto-saved files are placed to the 'reformat and cleanup' queue and will be processed on the next explicit save.

Automatically enforce style preferences for null-checking patterns on saving changes

  1. Press Ctrl+Alt+S to open the IDE settings and select Tools | Actions on Save.

  2. Select Reformat and Cleanup Code, choose your custom Code Cleanup profile and whether to apply it to the whole file or only to the changed lines.

  3. The next time you finish editing and save the file or all files , JetBrains Rider will clean up the affected files using the selected profile.

Configure preferences for null-checking patterns

Your null-checking pattern 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.

tip

Code style features that only change whitespaces, tabs, and line breaks are configurable in formatting preferences.

See also

Concepts

Procedures

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