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() == 0)
                    {
                        return;
                    }
                    
                    System.Drawing.Pen pen = new Pen(this.tipBorderColor, 1);
                    if (this.Focused || this.Text.Length > 0)
                    {
                        pen.Color = normalBorderColor;
                    }
                    //绘制边框 
                    System.Drawing.Graphics g = Graphics.FromHdc(hDC);
                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                    g.DrawRectangle(pen, 0, 0, this.Width - 1, this.Height - 1);
                    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);

        }
    }