Public variable in C#.net (Window Application)

Question

I want 2 define public variable in Window application of C#.net.
In V.B..net there is module in which we can define public variable which will remain public in whole project.
Bt in C#.net it changes in every form.It gives me default value of class (where i have define variable).
I have searched lot on google bt i have nt get appropriate Answer.
Plz help me out....