using System.Windows.Forms;

public class SynchronizedScrollRichTextBox : System.Windows.Forms.RichTextBox

{

    public SynchronizedScrollRichTextBox Synchronized { get; set; }

    public const int WM_VSCROLL = 0x115;

    public const int EM_LINESCROLL = 0xB6;

    protected override void WndProc(ref System.Windows.Forms.Message msg)

    {

        if (msg.Msg == WM_VSCROLL || msg.Msg == EM_LINESCROLL)

        {

            if (Synchronized != null)

            {

                Message message = msg;

                message.HWnd = Synchronized.Handle;

                Synchronized.PubWndProc(ref message);

            }

        }

        base.WndProc(ref msg);

    }

    public void PubWndProc(ref System.Windows.Forms.Message msg)

    {

        base.WndProc(ref msg);

    }

}