Compatibility with other languages.
I know that with .NET intermixing of languages is becoming a lot more common, but in this question, I'm not referring to that - I'm just talking about stand-alone everyday programs like a Hello World! program or something. I know the issues with C++ compiling under C compilers and vice versa, but how do the two get along with C#. I've never done any C# but I was just wandering, and I could be completely off - for all I know, C# could be based on some entirely different system, although it seems apparent that C# is C-derived.