Represents a way to bind to the password property while still being able to use the default PasswordBox

BindablePasswordBox.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

public class BindablePasswordBox : ContentControl
{
	private static void OnPasswordPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
	{
		var bindablePasswordBox = (BindablePasswordBox)d;
		bindablePasswordBox.OnPasswordPropertyChanged((string)e.OldValue, (string)e.NewValue);
	}

	public static readonly DependencyProperty PasswordProperty =
		DependencyProperty.Register("Password", typeof(string), typeof(BindablePasswordBox)
			, new FrameworkPropertyMetadata(string.Empty
				, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault | FrameworkPropertyMetadataOptions.Journal
				, new PropertyChangedCallback(BindablePasswordBox.OnPasswordPropertyChanged)
				, new CoerceValueCallback(/*CoerceText*/(d, v) => v == null ? (object)string.Empty : v)
				, true
				, UpdateSourceTrigger.LostFocus
			)
		);

	public string Password
	{
		get { return (string)GetValue(PasswordProperty); }
		set { SetValue(PasswordProperty, value); }
	}

	private PasswordBox _passwordBox;
	private RoutedEventHandler _passwordChanged;
	private bool _isInsidePasswordContentChange;

	public BindablePasswordBox()
	{
		Content = new PasswordBox();
	}

	protected override void OnContentChanged(object oldContent, object newContent)
	{
		Unsubscribe(oldContent);
		base.OnContentChanged(oldContent, newContent);
		Subscribe(newContent);
	}

	private void Subscribe(object newContent)
	{
		var passwordBox = newContent as PasswordBox;
		if (passwordBox != null)
		{
			_passwordBox = passwordBox;
			_passwordChanged = (sender, e) => {
				_isInsidePasswordContentChange = true;
				this.Password = passwordBox.Password;
				_isInsidePasswordContentChange = false;
			};
			passwordBox.PasswordChanged += _passwordChanged; // subscribe event handler
		}
	}

	private void Unsubscribe(object oldContent)
	{
		var passwordBox = oldContent as PasswordBox;
		if (passwordBox != null)
		{
			passwordBox.PasswordChanged -= _passwordChanged; // unsubscribe event handler
		}
	}

	private void OnPasswordPropertyChanged(string oldValue, string newValue)
	{
		if (_isInsidePasswordContentChange)
		{
			return;
		}
		var passwordBox = _passwordBox;
		if (passwordBox != null)
		{
			passwordBox.PasswordChanged -= _passwordChanged; // unsubscribe event handler
			passwordBox.Password = newValue;
			passwordBox.PasswordChanged += _passwordChanged; // resubscribe event handler
		}
	}
}