FATrace/FATrace.WPLApp/Models/PasswordBoxBehavior.cs

using Microsoft.Xaml.Behaviors;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;

namespace FATrace.WPLApp.Models
{
    public class PasswordBoxBehavior : Behavior<PasswordBox>
    {
        public static readonly DependencyProperty PasswordProperty =
            DependencyProperty.Register("Password", typeof(string), typeof(PasswordBoxBehavior),
                new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
                    OnPasswordPropertyChanged));

        private bool _isUpdating;

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

        private static void OnPasswordPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var behavior = d as PasswordBoxBehavior;
            if (behavior._isUpdating) return;

            if (behavior.AssociatedObject != null)
            {
                behavior._isUpdating = true;
                behavior.AssociatedObject.Password = e.NewValue?.ToString() ?? string.Empty;
                behavior._isUpdating = false;
            }
        }

        protected override void OnAttached()
        {
            base.OnAttached();
            AssociatedObject.PasswordChanged += OnPasswordBoxValueChanged;
        }

        protected override void OnDetaching()
        {
            AssociatedObject.PasswordChanged -= OnPasswordBoxValueChanged;
            base.OnDetaching();
        }

        private void OnPasswordBoxValueChanged(object sender, RoutedEventArgs e)
        {
            _isUpdating = true;
            Password = AssociatedObject.Password;
            _isUpdating = false;
        }
    }
}