static void Main()
{
Context c = new Context(new ConcreteStateA());
// Issue requests, which toggles state
c.Request();
c.Request();
c.Request();
c.Request();
}
public override void Handle(Context context)
{
context.State = new ConcreteStateB();
Console.WriteLine("Switching to ConcreteStateB!");
}
public abstract void Handle(Context context);
