In, .NET, there are no "global variables". And this is good: they are not really needed and are potentially dangerous; using them indicates bad style. In .NET, everything has its context.
The closest concept would be the
Singleton pattern, but even it should be used rarely, when it is really beneficial. You did not explain a single convincing reason for that. Please read about it:
http://en.wikipedia.org/wiki/Singleton_pattern[
^].
And I saw a number of bad implementations of the pattern. A good one in C# can be found here:
http://csharpindepth.com/Articles/General/Singleton.aspx[
^].
—SA