WPF---数据绑定之PasswordBox绑定

超、凢脫俗 2021-11-17 12:54 659阅读 0赞

#  #

**一、概述**

众所周知，绑定的源既可以是依赖属性也可以是普通的CLR属性，而**绑定的目标只能是依赖属性**。

控件PasswordBox的Password属性不是依赖属性，不可以作为绑定的目标与后台数据进行绑定，而在MVVM模式中，前台和后台的绑定是经常需要的，为了达到这种目的，我们可以借助附加属性来实现PasswordBox的Password属性的绑定。

**二、绑定思路**

思路如下：

1）定义一个PasswordBoxHelper类，在类中定义PasswordProperty、AttachProperty和IsUpdatingProperty三个附加属性以及相应的属性改变事件；

2）在AttachProperty的OnAttachPropertyChanged事件中添加PasswordBox的PasswordChanged事件处理程序，这样PasswordBox控件中输入密码的时候，就会触发PasswordBoxHelper类中PasswordChanged事件处理函数；

3）PasswordChanged事件处理函数执行的时候，把控件中的信息赋值给PasswordBoxHelper类中的依赖属性PasswordProperty；

**三、Demo**

using System.Windows;
    
    namespace PasswordBinding
    {
        /// <summary>
        /// Interaction logic for MainWindow.xaml
        /// </summary>
        public partial class MainWindow : Window
        {
            //private string password;
    
            //public string Password
            //{
            //    get { return password; }
            //    set { password = value; }
            //}
    
            public string Password//依赖属性具有自动通知的能力，不需要实现INotifi接口
            {
                get { return (string)GetValue(PasswordProperty); }
                set { SetValue(PasswordProperty, value); }
            }
    
            // Using a DependencyProperty as the backing store for Password.  This enables animation, styling, binding, etc...
            public static readonly DependencyProperty PasswordProperty =
                DependencyProperty.Register("Password", typeof(string), typeof(MainWindow), new PropertyMetadata(""));
    
    
            public MainWindow()
            {
                InitializeComponent();
                this.DataContext = this;
            }
    
            private void Button_Click(object sender, RoutedEventArgs e)
            {
                //tbl.Text = password;
                tbl.Text = PasswordBoxHelper.GetPassword(pwd);
            }
        }
    }

using System.Windows;
    using System.Windows.Controls;
    
    namespace PasswordBinding
    {
    
        public static class PasswordBoxHelper
        {
    
            public static readonly DependencyProperty PasswordProperty = DependencyProperty.RegisterAttached("Password", typeof(string), typeof(PasswordBoxHelper), 
                                                                                                              new FrameworkPropertyMetadata(string.Empty, OnPasswordPropertyChanged));
            public static readonly DependencyProperty AttachProperty = DependencyProperty.RegisterAttached("Attach", typeof(bool), typeof(PasswordBoxHelper), new PropertyMetadata(false, OnAttachPropertyChanged));
    
            private static readonly DependencyProperty IsUpdatingProperty = DependencyProperty.RegisterAttached("IsUpdating", typeof(bool), typeof(PasswordBoxHelper));
    
    
            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;
                passwordBox.PasswordChanged -= PasswordChanged;
                if (!(bool)GetIsUpdating(passwordBox))
                {
                    passwordBox.Password = (string)e.NewValue;
                }
                passwordBox.PasswordChanged += PasswordChanged;
            }
    
            private static void OnAttachPropertyChanged(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);
            }
        }
    }

![562297-20190719121250802-345987296.png][]

转载于:https://www.cnblogs.com/aijiao/p/11212509.html

[562297-20190719121250802-345987296.png]: /images/20211116/d63d840364bc4c31ac593d3a140b42ea.png