阻止控件重绘

//控件重绘
[DllImport("USER32.DLL ", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool SendMessage(
    IntPtr hWnd, // 目标窗口句柄   
    int Msg, // 消息
    bool wParam, // 第一个消息参数 false阻止 true不阻止
    int lParam );
const int WM_GETTEXT =0x000B;
SendMessage(this.Handle, WM_GETTEXT, false, 0);