What is the best or most interesting use of Extension Methods you've seen? [closed]

Answer 1

This is an extension method to centralize null checks before raising events.

public static class EventExtension
{
    public static void RaiseEvent(this EventHandler handler, object obj, T args) where T : EventArgs
    {
        EventHandler theHandler = handler;

        if (theHandler != null)
        {
            theHandler(obj, args);
        }
    }
}