By definition, you can only call a protected method from the declaring class or any of derived classes.
Strictly speaking, there is another way,
reflection, but: 1) this is a trick; 2) you should not get to such advanced topics before you make yourself confident with the fundamentals, which you don't know yet.
Please read:
http://msdn.microsoft.com/en-us/library/76453kax.aspx[
^].
Please, don't ask what to do if you cannot use such a derived class or the declaring class. The answer would be: the decision is up to you. It's possible that you should not use the protected method, or even need to radically fix your code design. Anyway, your related follow-up questions will be welcome.
—SA