private void cmdDelegateCallback_Click(object sender, System.EventArgs e)
	{
        //This method calls into a method of a Class1 instance, which in turn 
        //calls back into the client via a delegate.
        Class1 refClass1 = new Class1();

        //Create an instance of a delegate to represent the callback method
        Delegate1 d = new Delegate1(this.CallbackMethod);

        //Register the client, passing a reference to the delegate instance
        refClass1.RegisterDelegateForCallback(d);

        //Call the method which will in turn call back into the client
        refClass1.UseDelegateCallback();

        //Unregister the client
        refClass1.UnRegisterDelegateForCallback();
    }

delegate void Delegate1();
  public void RegisterDelegateForCallback(Delegate1 d)
    {
 	del1 = d;
    }

    public void UnRegisterDelegateForCallback()
    {
        del1 = null;
    }

    public void UseDelegateCallback()
	{
        if (del1 != null)
	{
            del1.BeginInvoke(null, null);
        }
    }