At present, there are 3 C# decompilation tools I have used: ILSpy (open source), dotPeek (open source), Reshaper
Reshaper, I used it at the beginning, as a plug-in for visual studio, but it consumes too much performance, once it is turned on, it gets stuck and cannot be used.
Download address: https://www.jetbrains.com/resharper/
ILSpy, I usually use it to look at the source code. Net source code, very lightweight
Download address: https://github.com/icsharpcode/ILSpy/releases
dotPeek, I use it to decompile some custom dll files, because I can't decompile them with ILSpy, and various errors are reported