我们发现我们无法绑定密码框的密码，PasswordBox 的 Password 不能绑定。 我们想做 MVVM ，我们需要绑定密码，不能使用前台 xaml.cs 监听 密码改变得到密码的值，传到 ViewModel 。 本文提供一个简单方法来绑定 WPF 的 PasswordBox 的 Password 。这种方法不仅在 WPF 可以使用，在 UWP 也可以使用。关于 UWP 绑定密码，可以在我博客 win10 uwp 绑定密码 查看。
我在网上找的很多大神给出的可以解决绑定密码的方法，下面是我找的一个简单方法。
首先需要新建一个类 PasswordHelper ，他是一个静态类，当然不是静态也没关系，但是一般写静态的可以让我们少犯错，因为我们所有属性等都是需要静态的。
public static class PasswordHelper { public static readonly DependencyProperty PasswordProperty = DependencyProperty.RegisterAttached("Password", typeof(string), typeof(PasswordHelper), new FrameworkPropertyMetadata(string.Empty, OnPasswordPropertyChanged));
public static readonly DependencyProperty AttachProperty = DependencyProperty.RegisterAttached("Attach", typeof(bool), typeof(PasswordHelper), new PropertyMetadata(false, Attach));
private static readonly DependencyProperty IsUpdatingProperty = DependencyProperty.RegisterAttached("IsUpdating", typeof(bool), typeof(PasswordHelper));
public static void SetAttach(DependencyObject dp, bool value) { dp.SetValue(AttachProperty, value); }
public static bool GetAttach(DependencyObject dp) { return (bool)dp.GetValue(AttachProperty); }
public static string GetPassword(DependencyObject dp) { return (string)dp.GetValue(PasswordProperty); }
public static void SetPassword(DependencyObject dp, string value) { dp.SetValue(PasswordProperty, value); }
private static bool GetIsUpdating(DependencyObject dp) { return (bool)dp.GetValue(IsUpdatingProperty); }
private static void SetIsUpdating(DependencyObject dp, bool value) { dp.SetValue(IsUpdatingProperty, value); }
private static void OnPasswordPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e) { PasswordBox passwordBox = sender as PasswordBox; if (passwordBox != null) { passwordBox.PasswordChanged -= PasswordChanged;
if (!(bool)GetIsUpdating(passwordBox)) { passwordBox.Password = (string)e.NewValue; } passwordBox.PasswordChanged += PasswordChanged; } }
private static void Attach(DependencyObject sender, DependencyPropertyChangedEventArgs e) { PasswordBox passwordBox = sender as PasswordBox;
if (passwordBox == null) return;
if ((bool)e.OldValue) { passwordBox.PasswordChanged -= PasswordChanged; }
if ((bool)e.NewValue) { passwordBox.PasswordChanged += PasswordChanged; } }
private static void PasswordChanged(object sender, RoutedEventArgs e) { PasswordBox passwordBox = sender as PasswordBox; if (passwordBox != null) { SetIsUpdating(passwordBox, true); SetPassword(passwordBox, passwordBox.Password); SetIsUpdating(passwordBox, false); } } }写完我们就可以使用他，使用很简单，在我们需要密码框的页面的xaml 上写两行新的代码就好。
<PasswordBox local:PasswordHelper.Attach="True" local:PasswordHelper.Password="{Binding Password, Mode=TwoWay}" Width="180" Style="{DynamicResource PasswordBoxStyle}"/>其中，Password 是 ViewModel 的PassWord，很简单我们把PasswordBox 绑定到ViewModel。
PASSWORDPROPERTY是附加属性，REGISTERATTACHED 就是注册附加。
我们附加属性是回调，当属性变化使用函数。
我们需要设置Attach，设置时调用static void Attach(DependencyObject sender, DependencyPropertyChangedEventArgs e)
在 Attach 触发，首先要判断设置的 sender 是不是 Password
PasswordBox passwordBox = sender as PasswordBox;
if (passwordBox == null) { return; }判断改变的值，Old是true还是false，如果是true，那么之前用了事件，我们要把事件
passwordBox.PasswordChanged -= PasswordChanged;如果之前是false，那么没绑定，我们不能删除。
判断要改变的，如果是true，我们就
passwordBox.PasswordChanged += PasswordChanged;如果不是，我们就不使用。
我们使用了是否存在密码修改就使用PasswordChanged函数。也就是设置了刚才的就可在密码变化使用PasswordChanged。
我们在PasswordChanged判断输入是不是PasswordBox，把密码传进PasswordProperty。
参见：http://www.wpftutorial.net/PasswordBox.html
还有一个简单方法
using System.Windows;using System.Windows.Controls;
namespace CustomControl{ public class BindablePasswordBox : Decorator { /// <summary> /// The password dependency property. /// </summary> public static readonly DependencyProperty PasswordProperty;
private bool isPreventCallback; private RoutedEventHandler savedCallback;
/// <summary> /// Static constructor to initialize the dependency properties. /// </summary> static BindablePasswordBox() { PasswordProperty = DependencyProperty.Register( "Password", typeof(string), typeof(BindablePasswordBox), new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, new PropertyChangedCallback(OnPasswordPropertyChanged)) ); }
/// <summary> /// Saves the password changed callback and sets the child element to the password box. /// </summary> public BindablePasswordBox() { savedCallback = HandlePasswordChanged;
PasswordBox passwordBox = new PasswordBox(); passwordBox.PasswordChanged += savedCallback; Child = passwordBox; }
/// <summary> /// The password dependency property. /// </summary> public string Password { get { return GetValue(PasswordProperty) as string; } set { SetValue(PasswordProperty, value); } }
/// <summary> /// Handles changes to the password dependency property. /// </summary> /// <param name="d">the dependency object</param> /// <param name="eventArgs">the event args</param> private static void OnPasswordPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs eventArgs) { BindablePasswordBox bindablePasswordBox = (BindablePasswordBox) d; PasswordBox passwordBox = (PasswordBox) bindablePasswordBox.Child;
if (bindablePasswordBox.isPreventCallback) { return; }
passwordBox.PasswordChanged -= bindablePasswordBox.savedCallback; passwordBox.Password = (eventArgs.NewValue != null) ? eventArgs.NewValue.ToString() : ""; passwordBox.PasswordChanged += bindablePasswordBox.savedCallback; }
/// <summary> /// Handles the password changed event. /// </summary> /// <param name="sender">the sender</param> /// <param name="eventArgs">the event args</param> private void HandlePasswordChanged(object sender, RoutedEventArgs eventArgs) { PasswordBox passwordBox = (PasswordBox) sender;
isPreventCallback = true; Password = passwordBox.Password; isPreventCallback = false; } }}
原文链接: http://blog.lindexi.com/post/WPF-%E7%BB%91%E5%AE%9A%E5%AF%86%E7%A0%81
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