ReSharper by Language: C#
ReSharper 2021.2 fully supports all C# versions up to C# 9.0. C# is the primary programming language ReSharper is intended for, and therefore all ReSharper features (excluding some features specific to other languages) are supported in C# (for more information, see ReSharper Features in Different Languages).
Change language version
By default, ReSharper automatically detects C# version based on the associated compiler. However, you can specify the target C# version explicitly for a project — right-click the project in the Solution Explorer, choose Edit project item properties from the context menu and use the C# Language Level selector.
To set the C# version for all projects in your solution, specify it in a Directory.Build.props file in your solution directory as described here.
Depending on the current C# version — whether it is detected automatically or set explicitly — ReSharper adjusts its features. For example, code inspection detects places in your code, which could be simplified using new language features.
Information on ReSharper features in C# is available in the following sections: