As you're already noticed, there isn't a Header concept for C#. Stuff that you normally define in C++ headers is packed into normal class files (*.cs) in C#, e.g. enum and stuff. You'd better be creating an own class file for each class. Use Visual Studios Folders to separate the .cs files by concern. This will normally also be reflected in the namespaces. To Access classes from different namespaces, use the "using" keyword in C#.
HTH, alex