TextBox 文本框水印文字

     #region TextBox 文本框水印文字
     /// <summary>
     /// 基于.NET 2.0的TextBox工具类
     /// </summary>
     public static class TextBoxToolV2 {
         private const int EM_SETCUEBANNER = 0x1501;
         [DllImport("user32.dll", CharSet = CharSet.Auto)]

         private static extern Int32 SendMessage
          (IntPtr hWnd, int msg, int wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);

         /// <summary>
         /// 为TextBox设置水印文字
         /// </summary>
         /// <param name="textBox">TextBox</param>
         /// <param name="watermark">水印文字</param>
         public static void SetWatermark(this TextBox textBox, string watermark) {
             SendMessage(textBox.Handle, EM_SETCUEBANNER, , watermark);
         }
         /// <summary>
         /// 清除水印文字
         /// </summary>
         /// <param name="textBox">TextBox</param>
         public static void ClearWatermark(this TextBox textBox) {
             SendMessage(textBox.Handle, EM_SETCUEBANNER, , string.Empty);
         }
     }

     #endregion