ReSharper 2020.3 Help

Code Syntax Style: Object Creation ('new()' vs 'new T()')

Starting with C# 9.0, you can you create objects with the target-typed new operator without explicit type specification when the type can be inferred, that is List<string> _myList = new(); instead of List<string> _myList = new List<string>();.

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

  • when created type is evident from usage (for example, in field initializations),

  • when created type is not evident (for example, in return statements).

ReSharper helps you enforce style preferences for object creation 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 object creation expressions

By default, ReSharper highlights type specifications as redundant in evident cases and helps removing them:

ReSharper syntax style inspection: Use target-typed new

On the other hand, in non-evident cases ReSharper suggests explicitly specifying the created type:

ReSharper syntax style inspection: Specify created type

If you prefer other styles for the new operator in your code, you can change the corresponding preferences.

Another option to enforce your preferences for object creation 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 object creation style with custom Code Cleanup profile

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

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

  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 object creation style ('new()' vs 'new T()') checkbox. Optionally, you can enable other code cleanup tasks in this profile.

  4. 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, 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 enforce style preferences for object creation 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 Control+Shift+Alt+F . . You can also create a custom cleanup profile that would combine arranging object creation expressions with other code style tasks.

Configure preferences for object creation expressions

Your object creation 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 Code Editing | C# | Syntax Style page of ReSharper options ( Alt+R, O ).

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

  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 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, see Manage and Share ReSharper Settings.

Applicability in different languages

This feature is supported in the following languages and technologies:

Language: C# Language: VB.NET Language: C++ Language: HTML Language: ASP.NET Language: Razor Language: JavaScript Language: TypeScript Language: CSS Language: XML Language: XAML Language: Resx Language: Build Scripts Language: Protobuf Language: JSON
Feature is available in C# Feature is not available in Visual Basic .NET Feature is not available in C++ Feature is not available in HTML Feature is not available in ASP.NET Feature is not available in Razor Feature is not available in JavaScript Feature is not available in TypeScript Feature is not available in CSS Feature is not available in XML Feature is not available in XAML Feature is not available in Resource files Feature is not available in build script files Feature is not available in Protobuf Feature is not available in JSON
Last modified: 08 December 2020