.net中如何让richtextbox隐藏光标

public class RichTextBoxEx : RichTextBox
{
    private readonly object mustHideCaretLocker = new object();

    private bool mustHideCaret;

    [DefaultValue(false)]
    public bool MustHideCaret
    {
        get
        {
            lock (this.mustHideCaretLocker)
                return this.mustHideCaret;
        }
        set
        {
            TabStop = false;
            if (value)
                SetHideCaret();
            else
                SetShowCaret();
        }
    }

    [DllImport("user32.dll")]
    private static extern int HideCaret(IntPtr hwnd);
    [DllImport("user32.dll", EntryPoint = "ShowCaret")]
    public static extern long ShowCaret(IntPtr hwnd);

    public RichTextBoxEx()
    {
    }

    private void SetHideCaret()
    {
        MouseDown += new MouseEventHandler(ReadOnlyRichTextBox_Mouse);
        MouseUp += new MouseEventHandler(ReadOnlyRichTextBox_Mouse);
        Resize += new EventHandler(ReadOnlyRichTextBox_Resize);
        HideCaret(Handle);
        lock (this.mustHideCaretLocker)
            this.mustHideCaret = true;
    }

    private void SetShowCaret()
    {
        try
        {
            MouseDown -= new MouseEventHandler(ReadOnlyRichTextBox_Mouse);
            MouseUp -= new MouseEventHandler(ReadOnlyRichTextBox_Mouse);
            Resize -= new EventHandler(ReadOnlyRichTextBox_Resize);
        }
        catch
        {
        }
        ShowCaret(Handle);
        lock (this.mustHideCaretLocker)
            this.mustHideCaret = false;
    }

    protected override void OnGotFocus(EventArgs e)
    {
        if (MustHideCaret)
            HideCaret(Handle);
    }

    protected override void OnEnter(EventArgs e)
    {
        if (MustHideCaret)
            HideCaret(Handle);
    }

    private void ReadOnlyRichTextBox_Mouse(object sender, System.Windows.Forms.MouseEventArgs e)
    {
        HideCaret(Handle);
    }

    private void ReadOnlyRichTextBox_Resize(object sender, System.EventArgs e)
    {
        HideCaret(Handle);
    }
}