ReSharper 2017.3 Help

Code Syntax Style: Implicit/Explicit Typing

Using implicitly typed local variables (also known as var keyword) introduced in C# 3.0 has become quite popular as it improves readability in many scenarios. By default, ReSharper also encourages using of var keyword, but preferences of its usage are flexibly configurable — for example, you can opt for using explicit types in specific cases or everywhere and ReSharper will help you enforce your preferences.

Enforcing preferences of using 'var' keyword

ReSharper checks all local variables for compliance with your preferences and if they do not comply, ReSharper highlights such declarations and suggests the corresponding quick-fix or fix in scope.

By default, ReSharper's preferences say that 'var' keyword is preferred:

'Var' usage quick-fix
If you change your preference, ReSharper will help you to use explicit types:
'Var' usage quick-fix

Another option to enforce preferences of 'var' keyword usage in a bulk mode is code cleanup. You can either run code cleanup with the default profile Default: Full Cleanup or run the cleanup with a custom profile solely targeted at your specific task as described below.

To apply preferences of using 'var' keyword with custom Code Cleanup profile

  • 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 drop-down list. For more information, see managing and sharing resharper settings.

If you want to enforce 'var' keyword usage setting without opening the Code Cleanup dialog, you can bind the created profile to the silent cleanup and run it simply by pressing Ctrl+Shift+Alt+F. You can also create a custom cleanup profile that would combine applying the preferences with other code style tasks.

Configuring preferences of using 'var' keyword

Your 'var' keyword usage 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.

To configure preferences of using 'var' keyword

  1. Modify settings in the 'var' usage in declarations category according to your coding practices/standards. You can set different preferences of using 'var' or explicit type for different types:
    • For built-in types - applies to C# built-in types.
    • For simple types - applies to types without generic parameters.
    • Elsewhere - applies to generic types.
    For each of these preferences you can opt for using 'var', explicit type, or 'var' when evident, which means that 'var' should be only used for variables initialized as creation of objects, arrays, and literals or explicit casts.
  2. 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 drop-down list. For more information, see managing and sharing resharper settings.

You can also change your preference of using 'var' keyword right in the editor, where a corresponding issue is highlighted:

To change preference of using 'var' keyword from the editor

  • In the action list, go to Inspection "Use preferred 'var' style" | Configure code style and then select a desired preference:
    Changing code style preference for 'var' keyword

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
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The instructions and examples given here address the use of the feature in C#. For details specific to other languages, see corresponding topics in the ReSharper by Language section.

Last modified: 22 February 2018

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