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);
                }
            }
        }

    }
}