Make 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, JetBrains Rider suggests that you make 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 JetBrains Rider to suggest 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), JetBrains Rider 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 Default: Full Cleanup profile or create and run a custom profile solely targeted at your specific task as described below.
To add the 'readonly' keyword to fields that only have read access
Go to the Code Cleanup settings page:.
Create a new profile as described in the To create a new custom cleanup profile section. In the Selected profile settings section for the new profile, tick the Make field read-only, if possible checkbox. Optionally, you can enable other code cleanup tasks in this profile.
Click Save 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 manage and share jetbrains rider settings.
Select the scope where you want to make fields readonly:
Set the caret anywhere in the file to make fields readonly to the file.
Select one or more items in the Solution Explorer to make fields readonly in the files under these nodes and their child items.
Choose Code | Code Cleanup in the main menu.
In the Code Cleanup dialog that opens, select the newly created profile.
Click OK. JetBrains Rider will make fields readonly in the selected scope.