WndProcメソッドを利用してUserControl上のコントロールで発生するメッセージを処理するには

class SampleControl : System.Windows.Forms.UserControl {
	public SampleControl() { ... }

	private class MessageFilter : IMessageFilter {
		private SampleControl owner;

		private MessageFilter() { throw new InvalidOperationException(); }
		public MessageFilter(SampleControl owner) {
			this.owner = owner;
		}

		[DllImport("user32.dll")]
		private static extern bool IsChild(IntPtr hParentWnd, IntPtr hWnd);

		bool IMessageFilter.PreFilterMessage(ref Message msg) {
			return
				!owner.IsDisposed                  &&
				 owner.Visible                     &&
				 owner.Enabled                     &&
				 IsChild(owner.Handle, msg.HWnd)   &&
				 owner.PreProcessChildControlMessage(ref msg);
		}
	}

	private MessageFilter messageFilter = null;
	private void AttachMessageFilter() {
		if(messageFilter == null) {
			messageFilter = new MessageFilter(this);
		}
		Application.AddMessageFilter(messageFilter);
	}
	private void DetachMessageFilter() {
		Application.RemoveMessageFilter(messageFilter);
	}

	protected override void OnHandleCreated(EventArgs e) {
		AttachMessageFilter();
		base.OnHandleCreated(e);
	}
	protected override void OnHandleDestroyed(EventArgs e) {
		DetachMessageFilter();
		base.OnHandleDestroyed(e);
	}

	protected virtual bool PreProcessChildControlMessage(ref Message msg) {
		return false;
	}
}