.NET Reflector Support: Can I decompile a whole assembly back to C# or VB source code?

Yes, absolutely.

You can use one of these add-ins to extract a .NET assembly to source:

Denis Bauer’s File Disassembler.

http://www.codeplex.com/FileGenReflector

You could even use these add-ins to convert from VB to C# or vice versa just by decompiling the compiled assembly into your desired language. If you’ve generated XML documentation FileDisassembler will even re-insert that documentation into the generated source code. Note that .NET Reflector’s source code generation is not always perfect, so you may have to do a little work to get the generated source to compile.