silverlight WPF 水纹文本框

silverlight3取消了watertextbox控件，只有自己实现了个，实现了和textbox一样的无差异使用，只需要设置defaulttext就可以了

 using System;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Media;
 
 namespace iLIS.Common.Controls
 {
     /// <summary>
     /// 自定义WatermarkedTextBox控件
     /// </summary>
     public class WatermarkedTextBox : TextBox
     {
         /// <summary>
         /// 水印文字
         /// </summary>
         public string DefaultText
         {
             get
             {
                 return (string)GetValue(DefaultTextProperty);
             }
             set
             {
                 SetValue(DefaultTextProperty, value);
             }
         }
         /// <summary>
         /// 文本框中的文字
         /// 文字为水印文字时返回空
         /// </summary>
         public string Text
         {
             get
             {
                 if (base.Text == DefaultText)
                 {
                     return string.Empty;
                 }
                 else
                 {
                     return base.Text;
                 }
             }
             set
             {
                 base.Text = value;
             }
         }
         /// <summary>
         /// 获取或设置一个用于描述前景色的画笔。
         /// 用于绘制控件的前景的画笔。默认值为 System.Windows.Media.Colors.Black。
         /// </summary>
         public new Brush Foreground
         {
             get
             {
                 return (Brush)GetValue(ForegroundProperty);
             }
             set
             {
                 SetValue(ForegroundProperty, value);
             }
         }
 
         // Using a DependencyProperty as the backing store for Foreground.  This enables animation, styling, binding, etc...
         public static new readonly DependencyProperty ForegroundProperty =
             DependencyProperty.Register("Foreground", typeof(Brush), typeof(WatermarkedTextBox), new PropertyMetadata((o, e) =>
             {
                 SolidColorBrush brush = e.NewValue as SolidColorBrush;
                 if (brush != null && brush.Color != Colors.Gray)
                 {
                     (o as WatermarkedTextBox).oldBrush = brush;
                 }
             }));
 
         private Brush oldBrush = new SolidColorBrush(Colors.Black);
         /// <summary>
         /// 默认文本
         /// </summary>
         public static readonly DependencyProperty DefaultTextProperty =
             DependencyProperty.Register("DefaultText", typeof(string), typeof(WatermarkedTextBox), new PropertyMetadata(""));
         public event TextChangedEventHandler WatermarkedTextChanged;
         /// <summary>
         /// 初始化 System.Windows.Controls.TextBox 类的新实例。
         /// </summary>
         public WatermarkedTextBox()
         {
             base.TextChanged += new TextChangedEventHandler(OnWatermarkedTextBox_TextChanged);
         }
 
         /// <summary>
         ///在派生类中重写后，每当应用程序代码或内部进程（如重新生成布局处理过程）调用 System.Windows.Controls.Control.ApplyTemplate()，都将调用此方法。
         ///简而言之，这意味着就在UI 元素在应用程序中显示前调用该方法。有关更多信息，请参见“备注”。
         /// </summary>
         public override void OnApplyTemplate()
         {
             this.Text = this.DefaultText;
             base.OnApplyTemplate();
             base.Foreground = new SolidColorBrush(Colors.Gray);
         }
         /// <summary>
         ///在 System.Windows.UIElement.GotFocus 事件发生之前调用。
         /// </summary>
         /// <param name="e">事件的数据</param>
         protected override void OnGotFocus(RoutedEventArgs e)
         {
             if (string.Equals(base.Text, this.DefaultText, StringComparison.OrdinalIgnoreCase))
             {
                 base.Text = string.Empty;
             }
             base.OnGotFocus(e);
         }
         /// <summary>
         ///在 System.Windows.UIElement.LostFocus 事件发生之前调用。
         /// </summary>
         /// <param name="e">事件的数据</param>
         protected override void OnLostFocus(RoutedEventArgs e)
         {
             if (string.IsNullOrEmpty(base.Text))
             {
                 base.Text = this.DefaultText;
                 base.Foreground = new SolidColorBrush(Colors.Gray);
             }
             base.OnLostFocus(e);
         }
         /// <summary>
         /// 文本改变时调用
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
         private void OnWatermarkedTextBox_TextChanged(object sender, TextChangedEventArgs e)
         {
             if (!string.Equals(base.Text, this.DefaultText, StringComparison.OrdinalIgnoreCase))
             {
                 base.Foreground = oldBrush;
                 if (this.WatermarkedTextChanged != null)
                 {
                     this.WatermarkedTextChanged(this, e);
                 }
             }
         }
 
     }
 }