1.自定义类

using System;using System.Net;using System.Windows;using System.Windows.Controls;using System.Windows.Documents;using System.Windows.Ink;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Animation;using System.Windows.Shapes;namespace EasySL.UI.Controls{    public class MaskTextBox : TextBox    {        #region MaskText        /// 
        /// view sort style, desc arrow        /// 
        public static readonly DependencyProperty MaskTextProperty = DependencyProperty.Register("MaskText",typeof(string), typeof(MaskTextBox), new PropertyMetadata(new PropertyChangedCallback(DisplayDataPropertyCallBack)));        public static void DisplayDataPropertyCallBack(object sender, DependencyPropertyChangedEventArgs args)        {        }        public string MaskText        {            get { return (string)GetValue(MaskTextProperty); }            set { SetValue(MaskTextProperty, value); }        }        #endregion                public MaskTextBox()        {            Loaded += (sender, args) =>            {                if (string.IsNullOrEmpty(base.Text))                {                    base.Text = MaskText;                    base.Foreground = new SolidColorBrush(Colors.Gray);                }            };            base.GotFocus += (sender, args) =>            {                base.Foreground = new SolidColorBrush(Colors.Black);                 if (base.Text == MaskText)                    base.Text = string.Empty;            };            base.LostFocus += (sender, args) =>            {                if (!string.IsNullOrEmpty(base.Text))                    return;                base.Text = MaskText;                base.Foreground = new SolidColorBrush(Colors.Gray);            };        }        public new string Text        {            get            {                if (base.Text == MaskText)                    return string.Empty;                else                    return base.Text;            }            set { base.Text = value; }       }    }}

2.在xaml里添加引用