WPF PasswordBox进行数据绑定方法
目录
- 问题描述
- 解决办法
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。
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; } }
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