重写TextBox实现显示提示信息

     /// <summary>
     /// TextBox提示信息
     /// </summary>
     /// <author>Tim_et</author>
     /// <description>为TextBox提供提示信息，有ToolTip方式，边框提示方式，ErrorProvider方式</description>
     [ToolboxItem(true)]
     [ToolboxBitmap("information.bmp")]
     public partial class TipTextBox : TextBox
     {
         /// <summary>
         /// 窗体句柄绘制
         /// </summary>
         /// <param name="hWnd"></param>
         /// <returns></returns>
         [System.Runtime.InteropServices.DllImport("user32.dll")]
         static extern IntPtr GetWindowDC(IntPtr hWnd);
         [System.Runtime.InteropServices.DllImport("user32.dll")]
         static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

         //private string pattern = @"^[0-9]*$";
         private int WM_PAINT = 0xF;
         private string tipText;
         private Color tipTextColor = Color.DarkGray;
         private bool isShowTipText = false;
         private Color tipBorderColor = Color.Red;
         private Color normalBorderColor = Color.DimGray;
         private bool isShowTipBorder = false;
         #region errorProvider
         private ErrorProvider errorProvider;
         private string errorMsg = string.Empty;
         /// <summary>
         /// 错误信息
         /// </summary>
         public string ErrorMsg
         {
             get { return errorMsg; }
             set { errorMsg = value; }
         }
         /// <summary>
         /// 闪烁风格
         /// </summary>
         public ErrorBlinkStyle BlinkStyle
         {
             get { return errorProvider.BlinkStyle; }
             set { errorProvider.BlinkStyle = value; }
         }
         /// <summary>
         /// 闪烁间隔
         /// </summary>
         public int BlinkRate
         {
             get { return errorProvider.BlinkRate; }
             set { errorProvider.BlinkRate = value; }
         }

         #endregion

         /// <summary>
         /// 提示信息内容
         /// </summary>
         [DefaultValue("")]
         public string TipText
         {
             get { return tipText; }
             set
             {
                 tipText = value;
                 base.Invalidate();
             }
         }
         /// <summary>
         /// 提示信息的颜色
         /// </summary>
         [DefaultValue(typeof(Color), "DarkGray")]
         public Color TipTextColor
         {
             get { return tipTextColor; }
             set
             {
                 tipTextColor = value;
                 base.Invalidate();
             }
         }
         /// <summary>
         /// 是否显示提示信息
         /// </summary>
         public bool IsShowTipText
         {
             get { return isShowTipText; }
             set { isShowTipText = value; }
         }
         /// <summary>
         /// 提示边框颜色
         /// </summary>
         public Color TipBorderColor
         {
             get { return tipBorderColor; }
             set { tipBorderColor = value; }
         }
         /// <summary>
         /// 正常时颜色（无需提示时）
         /// </summary>
         public Color NormalBorderColor
         {
             get { return normalBorderColor; }
             set { normalBorderColor = value; }
         }
         /// <summary>
         /// 是否显示提示边框
         /// </summary>
         public bool IsShowTipBorder
         {
             get { return isShowTipBorder; }
             set { isShowTipBorder = value; }
         }

         public TipTextBox()
             : base()
         {
             errorProvider = new ErrorProvider();
         }

         protected override void WndProc(ref Message m)
         {

             base.WndProc(ref m);

             if (m.Msg == WM_PAINT || m.Msg == 0x133)
             {
                 if (isShowTipBorder)
                 {
                     IntPtr hDC = GetWindowDC(m.HWnd);
                     if (hDC.ToInt32() == )
                     {
                         return;
                     }

                     System.Drawing.Pen pen = new Pen(this.tipBorderColor, );
                     if (this.Focused || this.Text.Length > )
                     {
                         pen.Color = normalBorderColor;
                     }
                     //绘制边框
                     System.Drawing.Graphics g = Graphics.FromHdc(hDC);
                     g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                     g.DrawRectangle(pen, , , this.Width - , this.Height - );
                     pen.Dispose();
                     m.Result = IntPtr.Zero;
                     //释放
                     ReleaseDC(m.HWnd, hDC);
                 }

                 if (IsShowTipText)
                 {
                     ///使用TextRenderer绘制底层的显示字样
                     using (Graphics graphics = Graphics.FromHwnd(this.Handle))
                     {
                         if (string.IsNullOrEmpty(this.Text) && !string.IsNullOrEmpty(TipText) && !Focused)
                         {
                             TextFormatFlags textFormatFlags = TextFormatFlags.EndEllipsis | TextFormatFlags.VerticalCenter;
                             if (this.RightToLeft == RightToLeft.Yes)
                             {
                                 textFormatFlags |= TextFormatFlags.RightToLeft | TextFormatFlags.Right;
                             }
                             TextRenderer.DrawText(graphics, TipText, this.Font, base.ClientRectangle, TipTextColor, textFormatFlags);
                         }
                     }
                 }

             }
         }

         /// <summary>
         /// 显示errorProvider
         /// </summary>
         /// <param name="msg"></param>
         public void ShowErrorProvider(string msg)
         {
             errorProvider.SetError(this, msg);
         }

         private void InitializeComponent()
         {
             this.SuspendLayout();
             this.ResumeLayout(false);

         }
     }