Trips&Ticks: Do you know how you can unsubscribe from anonymous method?

Anonymous Methods is a useful feature which we receive in Framework 2.0. It allows to easy pass a small code block as a delegate parameter (you can set a large block code but this code will be harmful because it is complex and isn't clear for perception). For example:

button1.Click += delegate
{
 MessageBox.Show( "Anonymous" );
};

But I have one trouble. What can I do if I want to unsubscribe from event. Seems it is subscribed finally, isn't it?.. Noup! If we declare instance of delegate before define we can unsubscribe a event from this delegate in the code block. For example:

EventHandler handler = null;

handler = delegate
{
 MessageBox.Show( "Anonymous" );
 button2.Click -= handler;
};

button2.Click += handler;

So if we click on button1 we receive message box always. If we click on button2 we receive message box once.