Making Fields Readonly
It is often reasonable to use the 'readonly' modifier for fields that are assigned in the declaration or in a constructor and only have read usages. By default, ReSharper suggests you making a field readonly if the above conditions are met. It highlights such fields and suggests the corresponding quick-fix or fix in scope:

If you do not want ReSharper to suggest you this, you can disable the code inspection that detects it (Field can be made readonly).
The reverse functionality is also available. If you decide to change a readonly field later in your code (which leads to a compiler error), ReSharper detects the error and suggests fixing it by removing the 'readonly' keyword from the field:

Another option to make fields readonly 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 add the 'readonly' keyword to fields that only have read access
- Open the Code Cleanup options: .
- Create a new profile as described in the Code Cleanup section. In the Selected profile settings section for the new profile, tick the Make field read-only, if possible check box.
- 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.
- Select the scope where you want to make fields readonly:
- Do one of the following:
- In the Code Cleanup dialog that opens, select the newly created profile.
- Click Run. ReSharper will make fields readonly in the selected scope.
If you want to make fields readonly 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 making fields readonly with other code style tasks.
This feature is supported in the following languages/technologies:
See Also
Procedures:
- Naming Style
- Managing and Applying Code Formatting Rules
- File and Type Layout
- File Header Style
- Code Syntax Style: Namespace Imports
- Code Syntax Style: Implicit/Explicit Typing
- Using Auto-Properties
- Making Fields Readonly
- Code Syntax Style: Multiple Attributes
- Code Syntax Style: Modifiers
- Code Syntax Style: Optional Member Qualifiers
- Reformatting XML Doc Comments
- Removing Code Redundancies