WPF PasswordBox进行数据绑定方法_C#

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。

问题描述

PasswordBox的Password属性不是依赖属性，因此无法进行数据绑定。

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。

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									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：

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									// 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：

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									// 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; }

									}