Create a Context Action

What you should know beforehand:

Examples (?):

ToLowerCaseContextAction.cs

The purpose of context actions is to quickly introduce a minor change to the code, like changing access modifiers, convert foreach to for, and so on. When a context action is available for the current caret position, ReSharper displays the "hummer" action indicator. The list of possible context actions is displayed after a user presses Alt+Enter.

For example, let's create a very simple context action that will be applicable to variable declarations. If a variable name contains any character in uppercase, the context action will suggest to convert the name to lowercase (of course, from the point of functionality, such action is absolutely useless).

[ContextAction(Name = "ToLowerCase", Description = "Convert the text to lowercase", Group = "C#", Disabled = false,
    Priority = 1)]
public class ToLowerCaseContextAction : ContextActionBase
{
    private readonly IVariableDeclaration _nodeUnderCaret;
 
    public ToLowerCaseContextAction(LanguageIndependentContextActionDataProvider dataProvider)
    {
        _nodeUnderCaret = dataProvider.GetSelectedElement<IVariableDeclaration>();
    }
 
 
    protected override Action<ITextControl> ExecutePsiTransaction(ISolution solution, IProgressIndicator progress)
    {
        return textControl =>
        {
            var newText = _nodeUnderCaret.DeclaredName.ToLower();
            RenameRefactoringService.Rename(solution,
                new RenameDataProvider((IDeclaredElement) _nodeUnderCaret, newText), textControl);
        };
    }
 
    public override string Text => "Convert to lowercase";
 
    public override bool IsAvailable(IUserDataHolder cache)
    {
        var nodeText = _nodeUnderCaret?.DeclaredName;
        var containsUpperCase = nodeText != null && nodeText.Any(char.IsUpper);
        return containsUpperCase;
    }
}

Notes

The easiest way to create a context action is to inherit from the ContextActionBase class.
The context action class must be marked with the ContextAction attribute:
- Group defines the scope of the action (C# files in our case).
- Disabled specifies whether the action is disabled by default.
- Priority sets the position of the action in the actions list.
The context data provider LanguageIndependentContextActionDataProvider obtained in the constructor provides a super-helpful method GetSelectedElement that returns the tree node under the caret. The provider has also methods that allow you to get current offset, selection range and so on.
The Text property defines the text that will be shown in the actions list.
IsAvailable is used to check whether the action is available for the current caret position. If false, the action is not shown in the list of possible context actions.
ExecutePsiTransaction returns the action that is executed when the context action is selected.
Note that we use RenameRefactoringService to change variable's name. The service performs seamless renaming of a variable everywhere in the code.

Last modified: 04 July 2023