MonoDevelop - MonoDevelop enables developers to write desktop and web applications on Linux, Windows and Mac OS X.
ILSpy - ICSharpCode. Decompiler. Console..
Visual Studio Code - Build and debug modern web and cloud applications, by Microsoft
dnSpy - .NET assembly editor, decompiler, and debugger
Rider - Rider is a cross-platform .NET IDE based on the IntelliJ platform and ReSharper.
.NET Reflector - .