Code inspection: Redundant using directive

Unnecessary using directives are quite common. Whenever you create, say, a WinForms window, Visual Studio preemptively adds a large number of using directives in your code file. Since ReSharper is able to determine which using references are actually used in the file and which are redundant, it reports the problem, offering an option to remove the unnecessary directives.

If your project is targeting C# 10.0 or later, you may see a using directive highlighted as redundant in a file where symbols from the referenced namespace are actually used. This means that the namespace is referenced elsewhere in the project via a global using directive.