Storing a method as a member variable of a class

I have this as one of my members of the class 'KeyEvent':

private delegate void eventmethod();

And the constructor:

public KeyEvent(eventmethod D) 
{
    D();
}

What I want to do is instead of calling D() there, I want to store that method (D) as a member variable of KeyEvent, so something like:

stored_method = D();

And then later in another method of KeyEvent, do something like:

stored_method();

How can I do this?