本文介绍下PasswordBox进行数据绑定的方法，本文参考链接。
本文完整示例程序见GitHub。
PasswordBox的Password属性不是依赖属性，因此无法进行数据绑定。
该问题的解决办法有多种，本文介绍如何通过添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，但由于某种需求附加到该对象上，通过附加属性可以实现将属性与宿主解耦的目的。附加属性本质上就是依赖属性，只是它们在属性包装器和注册时有区别。注册附加属性使用RegisterAttached方法，注册依赖属性使用Register方法，这两个方法的参数差别并不大。
首先添加一个PasswordBoxBindingHelper类，该类包含一个附加属性（snippet：propa+两次tab），通过设置该属性的PropertyChangedCallback将改变通知到PasswordBox.Password，并通过添加对PasswordBox.PasswordChanged事件的响应来响应PasswordBox.Password的改变。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);
}
然后在View中使用该附加属性进行数据绑定，本文示例中主窗口包含一个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="查看密码" Command="{Binding ClickedCommand}"/>
</StackPanel>
</Grid>
</Window>
//xaml.cs 设置绑定源
public MainWindow()
{
InitializeComponent();
this.DataContext = new MainWindowViewModel();
}
最后创建ViewModel进行逻辑处理：
// ViewModel
public class MainWindowViewModel : INotifyPropertyChanged
{
public string Password
{
get => _password;
set
{
_password = value;
OnPropertyChanged();
}
}
public DelegateCommand ClickedCommand => _clickedCommand ?? (_clickedCommand = new DelegateCommand { ExecuteAction = OnClicked });
// 使用CallerMemberName特性简化代码，并可以避免手动输入错误
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ICommand
public 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; }
}
