How can I enumerate all managed threads in C#?

This sounds like a duplicate of "How to enumerate threads in .NET using the Name property?" - If so, the short answer is "keep track of your own threads yourself" - i.e. in a List<Thread> or similar.

Debuggers are often able to do things "normal" code can't. You'd probably find that you can do this if you use the profiling/debugging API, but I don't believe you can do it from "normal" .NET code.