There is no Session variables in windows forms.You can try this concept
Create a Static class that holds the User name and password and any other variables need in entire application.
Eg:
public static class LogginInformations
{
public static string UserID;
}
Now you can access the UserID from anywhere in your code, or set a value from any where.
For more information look on here.
http://msdn.microsoft.com/en-us/library/79b3xss3(v=vs.80).aspx[
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