本文介绍下PasswordBox进行数据绑定的办法，本文参考链接。

本文残缺示例程序见GitHub。

问题形容

PasswordBox的Password属性不是依赖属性，因而无奈进行数据绑定。

解决办法

该问题的解决办法有多种，本文介绍如何通过增加附加属性解决该问题。

附加属性是说一个属性本不属于某个对象，但因为某种需要附加到该对象上，通过附加属性能够实现将属性与宿主解耦的目标。附加属性实质上就是依赖属性，只是它们在属性包装器和注册时有区别。注册附加属性应用RegisterAttached办法，注册依赖属性应用Register办法，这两个办法的参数差异并不大。

首先增加一个PasswordBoxBindingHelper类，该类蕴含一个附加属性（snippet：propa+两次tab），通过设置该属性的PropertyChangedCallback将扭转告诉到PasswordBox.Password，并通过增加对PasswordBox.PasswordChanged事件的响应来响应PasswordBox.Password的扭转。有了该附加属性，即可进行数据绑定。

public static string GetPasswordContent(DependencyObject obj) => (string)obj.GetValue(PasswordContentProperty);public static void SetPasswordContent(DependencyObject obj, string value) => obj.SetValue(PasswordContentProperty, value);public static readonly DependencyProperty PasswordContentProperty =    DependencyProperty.RegisterAttached("PasswordContent", typeof(string), typeof(PasswordBoxBindingHelper),    new PropertyMetadata(string.Empty, OnPasswordContentPropertyChanged));private static void OnPasswordContentPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){    var box = d as PasswordBox;    box.PasswordChanged -= OnPasswordChanged;    var password = (string)e.NewValue;    if (box != null && box.Password != password)        box.Password = password;    box.PasswordChanged += OnPasswordChanged;}private static void OnPasswordChanged(object sender, RoutedEventArgs e){    var box = sender as PasswordBox;    SetPasswordContent(box, box.Password);}

而后在View中应用该附加属性进行数据绑定，本文示例中主窗口蕴含一个PasswordBox控件及一个Button按钮：

// xaml 绑定附加属性<Window ...        xmlns:local="clr-namespace:PasswordBoxBinding"        Title="PasswordBoxBinding" Height="300" Width="450" WindowStartupLocation="CenterScreen">    <Grid>        <StackPanel HorizontalAlignment="Center" Orientation="Horizontal">            <PasswordBox MinWidth="200" Height="30" BorderBrush="LightGray" BorderThickness="2"                         local:PasswordBoxBindingHelper.PasswordContent="{Binding Password,Mode=TwoWay}"/>            <Rectangle Width="20"/>            <Button Width="80" Height="30" Content="查看明码" Command="{Binding ClickedCommand}"/>        </StackPanel>    </Grid></Window>//xaml.cs 设置绑定源public MainWindow(){    InitializeComponent();    this.DataContext = new MainWindowViewModel();}

最初创立ViewModel进行逻辑解决：

// ViewModelpublic class MainWindowViewModel : INotifyPropertyChanged{    public string Password    {        get => _password;        set        {            _password = value;            OnPropertyChanged();        }    }    public DelegateCommand ClickedCommand => _clickedCommand ?? (_clickedCommand = new DelegateCommand { ExecuteAction = OnClicked });    // 应用CallerMemberName个性简化代码，并能够防止手动输出谬误    public void OnPropertyChanged([CallerMemberName] string name = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));    private void OnClicked(object o) => MessageBox.Show($"password: {Password}");    public event PropertyChangedEventHandler PropertyChanged;    private DelegateCommand _clickedCommand;    private string _password;}// 实现ICommandpublic class DelegateCommand : ICommand{    public bool CanExecute(object parameter) => CanExecuteAction?.Invoke(parameter) ?? true;    public void Execute(object parameter) => ExecuteAction?.Invoke(parameter);    public event EventHandler CanExecuteChanged;    public Action<object> ExecuteAction { get; set; }    public Func<object, bool> CanExecuteAction { get; set; }}