Something

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    public delegate void SomeEvent( object sender, EventArgs e );

    class Button
    {
        public event SomeEvent EventRecieved;

        public void FireClick()
        {
            if ( EventRecieved != null )
                EventRecieved( this, EventArgs.Empty );
        }
    }

    class Program
    {
        static void Main( string[] args )
        {
            Button b = new Button();

            b.EventRecieved += new SomeEvent( ImageHandler.HandleImageChange );

            b.FireClick(); // again, can be called, e.g., from UI thread
        }
    }

    public class ImageHandler
    {
        public static void HandleImageChange(object sender, EventArgs e )
        {
            Console.WriteLine( "changed" );
        }
    }
}