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Bindable WPF PasswordBox (AttachedProperty)

Out of the box you can't bind to the WPF PasswordBox's password property. This is done for security reason's. I think it's a bit overkill for most applications so I searched for a solution.

I found one here. The PasswordHelper is attached to the password box by calling the PasswordHelper.Attach property. The attached property PasswordHelper.Password provides a bindable copy of the original password property of the PasswordBox control.

The PasswordHelper class:

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)
        return;

      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;
      SetIsUpdating(passwordBox, true);
      SetPassword(passwordBox, passwordBox.Password);
      SetIsUpdating(passwordBox, false);
    }
  }

And in the XAML of your PasswordBox:

<PasswordBox x:Name="passwordBoxPwd"
             UserControls:PasswordHelper.Attach="True"
             UserControls:PasswordHelper.Password="{Binding MailPwd, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
             Margin="0 5 5 5"/>

I use it like this in my application and it works perfectly!