WPF中PasswordBox控件的Password属性的数据绑定

英文原文：http://www.wpftutorial.net/PasswordBox.html

中文原文：http://blog.csdn.net/oyi319/article/details/6551532

WPF的PasswordBox控件的Password属性不是依赖属性，无法直接进行数据绑定，为使其在MVVM模式中正常使用，可以为PasswordBox增加一个助手类，代码如下：

注：代码摘自：http://www.wpftutorial.net/PasswordBox.html

 1 using System.Windows;

 2 using System.Windows.Controls;

 3 namespace Oyi319.Helper

 4 {

 5     /// <summary>

 6     /// 为PasswordBox控件的Password增加绑定功能

 7     /// </summary>

 8     public static class PasswordBoxHelper

 9     {

10         public static readonly DependencyProperty PasswordProperty =

11             DependencyProperty.RegisterAttached("Password",

12             typeof(string), typeof(PasswordBoxHelper),

13             new FrameworkPropertyMetadata(string.Empty, OnPasswordPropertyChanged));

14         public static readonly DependencyProperty AttachProperty =

15             DependencyProperty.RegisterAttached("Attach",

16             typeof(bool), typeof(PasswordBoxHelper), new PropertyMetadata(false, Attach));

17         private static readonly DependencyProperty IsUpdatingProperty =

18            DependencyProperty.RegisterAttached("IsUpdating", typeof(bool),

19            typeof(PasswordBoxHelper));

20 

21         public static void SetAttach(DependencyObject dp, bool value)

22         {

23             dp.SetValue(AttachProperty, value);

24         }

25         public static bool GetAttach(DependencyObject dp)

26         {

27             return (bool)dp.GetValue(AttachProperty);

28         }

29         public static string GetPassword(DependencyObject dp)

30         {

31             return (string)dp.GetValue(PasswordProperty);

32         }

33         public static void SetPassword(DependencyObject dp, string value)

34         {

35             dp.SetValue(PasswordProperty, value);

36         }

37         private static bool GetIsUpdating(DependencyObject dp)

38         {

39             return (bool)dp.GetValue(IsUpdatingProperty);

40         }

41         private static void SetIsUpdating(DependencyObject dp, bool value)

42         {

43             dp.SetValue(IsUpdatingProperty, value);

44         }

45         private static void OnPasswordPropertyChanged(DependencyObject sender,

46             DependencyPropertyChangedEventArgs e)

47         {

48             PasswordBox passwordBox = sender as PasswordBox;

49             passwordBox.PasswordChanged -= PasswordChanged;

50             if (!(bool)GetIsUpdating(passwordBox))

51             {

52                 passwordBox.Password = (string)e.NewValue;

53             }

54             passwordBox.PasswordChanged += PasswordChanged;

55         }

56         private static void Attach(DependencyObject sender,

57             DependencyPropertyChangedEventArgs e)

58         {

59             PasswordBox passwordBox = sender as PasswordBox;

60             if (passwordBox == null)

61                 return;

62             if ((bool)e.OldValue)

63             {

64                 passwordBox.PasswordChanged -= PasswordChanged;

65             }

66             if ((bool)e.NewValue)

67             {

68                 passwordBox.PasswordChanged += PasswordChanged;

69             }

70         }

71         private static void PasswordChanged(object sender, RoutedEventArgs e)

72         {

73             PasswordBox passwordBox = sender as PasswordBox;

74             SetIsUpdating(passwordBox, true);

75             SetPassword(passwordBox, passwordBox.Password);

76             SetIsUpdating(passwordBox, false);

77         }

78     }

79 }

那么XAML绑定代码如下：

1 <PasswordBox Helper:PasswordBoxHelper.Attach="True" Helper:PasswordBoxHelper.Password="{Binding Path=Password,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" />

MVVM模式XAML窗口声明代码如下：

 1 <Window

 2     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

 3     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

 4     xmlns:Helper="clr-namespace:Oyi319.Helper" 

 5     xmlns:ViewModels="clr-namespace:Oyi319.ViewModels"

 6     x:Class="Oyi319.Views.Login"

 7     x:Name="Window"

 8     Title="Login"

 9     FocusManager.FocusedElement="{Binding ElementName=txt_UserName}" >

10     <Window.DataContext>

11         <ViewModels:LoginViewModel />

12     </Window.DataContext>

13 </Window>