ReSharper 2016.3 Help

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.

In this topic:

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 code cleanup

  1. Open the Code Cleanup options: ReSharper | Options | Code Editing | Code Cleanup.
  2. Create a new profile as described in the Configuring Code Cleanup section. In the Selected profile settings section for the new profile tick the Enforce 'var' keyword usage settings check box.
  3. 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.
  4. 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.
  5. Do one of the following:
    • Press Ctrl+Alt+F or choose ReSharper | Edit | Cleanup Code in the main menu .
    • Right-click anywhere in the text editor or right-click the selection and choose Cleanup Code in the context menu.
  6. In the Code Cleanup dialog that opens, select the newly created profile in the Available Profiles area.
  7. Click Run. ReSharper will enforce your preferences in the selected scope.

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 shared 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. Go to the Code Editing | C# | Code Style page of ReSharper options.
  2. 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.
  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 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

  1. Set the caret to a code issue highlighted by a ReSharper's inspection.
  2. Press Alt+Enter or click on the action indicator to the left of the caret to open the action list.
  3. In the action list, choose Inspection "Use preferred 'var' style" | Configure code style and then select a desired preference:
    Changing code style preference for 'var' keyword
  4. Your change will be saved using the smart save logic.
  5. If you need to save the modified style preference in a shared settings layer, click on the Configure code style menu item or press Enter when it is selected. ReSharper will open the Code Editing | C# | Code Style page of ReSharper options where you can modify your preference as needed, click Save To and then choose the desired settings layer.

This feature is supported in the following languages/technologies:

C# VB.NET C++ HTML ASPX Razor JavaScript TypeScript CSS XML XAML RESX Build Scripts Protobuf 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. Specifically:

See Also

Last modified: 3 April 2017