FATrace/FATrace.WPLApp/Utils/PasswordBoxAssistant.cs

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

namespace FATrace.WPLApp.Utils
{
    /// <summary>
    /// 允许将 PasswordBox 的 Password 与 ViewModel 绑定
    /// 用法：
    ///   <PasswordBox utils:PasswordBoxAssistant.BindPassword="True"
    ///                utils:PasswordBoxAssistant.BoundPassword="{Binding Password, Mode=TwoWay}" />
    /// </summary>
    public static class PasswordBoxAssistant
    {
        public static readonly DependencyProperty BoundPasswordProperty =
            DependencyProperty.RegisterAttached("BoundPassword", typeof(string), typeof(PasswordBoxAssistant), new PropertyMetadata(string.Empty, OnBoundPasswordChanged));

        public static readonly DependencyProperty BindPasswordProperty =
            DependencyProperty.RegisterAttached("BindPassword", typeof(bool), typeof(PasswordBoxAssistant), new PropertyMetadata(false, OnBindPasswordChanged));

        private static readonly DependencyProperty IsUpdatingProperty =
            DependencyProperty.RegisterAttached("IsUpdating", typeof(bool), typeof(PasswordBoxAssistant));

        public static string GetBoundPassword(DependencyObject dp) => (string)dp.GetValue(BoundPasswordProperty);
        public static void SetBoundPassword(DependencyObject dp, string value) => dp.SetValue(BoundPasswordProperty, value);

        public static bool GetBindPassword(DependencyObject dp) => (bool)dp.GetValue(BindPasswordProperty);
        public static void SetBindPassword(DependencyObject dp, bool value) => dp.SetValue(BindPasswordProperty, value);

        private static bool GetIsUpdating(DependencyObject dp) => (bool)dp.GetValue(IsUpdatingProperty);
        private static void SetIsUpdating(DependencyObject dp, bool value) => dp.SetValue(IsUpdatingProperty, value);

        private static void OnBoundPasswordChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
        {
            if (dp is PasswordBox passwordBox)
            {
                passwordBox.PasswordChanged -= HandlePasswordChanged;
                if (!(bool)GetIsUpdating(passwordBox))
                {
                    passwordBox.Password = e.NewValue?.ToString() ?? string.Empty;
                }
                passwordBox.PasswordChanged += HandlePasswordChanged;
            }
        }

        private static void OnBindPasswordChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
        {
            if (dp is PasswordBox passwordBox)
            {
                bool wasBound = (bool)(e.OldValue ?? false);
                bool needBind = (bool)(e.NewValue ?? false);

                if (wasBound)
                {
                    passwordBox.PasswordChanged -= HandlePasswordChanged;
                }
                if (needBind)
                {
                    passwordBox.PasswordChanged += HandlePasswordChanged;
                }
            }
        }

        private static void HandlePasswordChanged(object sender, RoutedEventArgs e)
        {
            if (sender is PasswordBox passwordBox)
            {
                SetIsUpdating(passwordBox, true);
                SetBoundPassword(passwordBox, passwordBox.Password);
                SetIsUpdating(passwordBox, false);
            }
        }
    }
}