自定义控件之带水印的Textbox

代码地址：

http://download.csdn.net/detail/u010312811/9553195

Windows消息处理：

http://www.cnblogs.com/imstrive/p/5596030.html

1.私有变量

 //水印文字
 private string _waterText = String.Empty;
 //水印颜色
 private Color _waterColor = Color.DarkGray;

2.属性

 /// <summary>
 /// 水印文字
 /// </summary>
 [Description("水印文字"),Category("SLT")]
 public string WaterText
 {
     get { return _waterText; }
     set { _waterText = value; }
 }
 /// <summary>
 /// 水印颜色
 /// </summary>
 [Description("水印文字"),Category("SLT")]
 public Color WaterColor
 {
     get { return _waterColor; }
     set { _waterColor = value; }
 }

3.Override Methods

 protected override void WndProc(ref Message m)
 {
     base.WndProc(ref m);

     if (m.Msg == (int)WindowsMessage.WM_PAINT)
     {
         WmPaintWater(ref m);
     }
 }

4.方法

 private void WmPaintWater(ref Message m)
 {
     //获取控件绑定到的窗口句柄
     using (Graphics g = Graphics.FromHwnd(base.Handle))
     {
         if (string.IsNullOrEmpty(this.Text) && !String.IsNullOrEmpty(this.WaterText) && !this.Focused)
         {
             TextFormatFlags flags = TextFormatFlags.EndEllipsis | TextFormatFlags.VerticalCenter;
             TextRenderer.DrawText(g, WaterText, this.Font, this.ClientRectangle, WaterColor, flags);
         }
     }
 }