PasswordBoxでデータバインド

【参考】http://garafu.blogspot.jp/2014/09/wcf-passwordbox.html
セキュリティの問題から基本的には非推奨
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利用方法
<PasswordBox [namespace]:PasswordBoxHelper.Password = {Binding Target}/>


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【PasswordBoxHelper.cs】

namespace WpfPasswordBox

{

    using System.Windows;

    using System.Windows.Controls;

    public class PasswordBoxHelper : DependencyObject

    {

        public static readonly DependencyProperty IsAttachedProperty = DependencyProperty.RegisterAttached(

            "IsAttached",

            typeof(bool),

            typeof(PasswordBoxHelper),

            new FrameworkPropertyMetadata(false, PasswordBoxHelper.IsAttachedProperty_Changed));

        public static readonly DependencyProperty PasswordProperty = DependencyProperty.RegisterAttached(

            "Password",

            typeof(string),

            typeof(PasswordBoxHelper),

            new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, PasswordBoxHelper.PasswordProperty_Changed));

        public static bool GetIsAttached(DependencyObject dp)

        {

            return (bool)dp.GetValue(PasswordBoxHelper.IsAttachedProperty);

        }

        public static string GetPassword(DependencyObject dp)

        {

            return (string)dp.GetValue(PasswordBoxHelper.PasswordProperty);

        }

        public static void SetIsAttached(DependencyObject dp, bool value)

        {

            dp.SetValue(PasswordBoxHelper.IsAttachedProperty, value);

        }

        public static void SetPassword(DependencyObject dp, string value)

        {

            dp.SetValue(PasswordBoxHelper.PasswordProperty, value);

        }

        private static void IsAttachedProperty_Changed(DependencyObject sender, DependencyPropertyChangedEventArgs e)

        {

            var passwordBox = sender as PasswordBox;

            if ((bool)e.OldValue)

            {

                passwordBox.PasswordChanged -= PasswordBoxHelper.PasswordBox_PasswordChanged;

            }

            if ((bool)e.NewValue)

            {

                passwordBox.PasswordChanged += PasswordBoxHelper.PasswordBox_PasswordChanged;

            }

        }

        private static void PasswordBox_PasswordChanged(object sender, RoutedEventArgs e)

        {

            var passwordBox = sender as PasswordBox;

            PasswordBoxHelper.SetPassword(passwordBox, passwordBox.Password);

        }

        private static void PasswordProperty_Changed(DependencyObject sender, DependencyPropertyChangedEventArgs e)

        {

            var passwordBox = sender as PasswordBox;

            var newPassword = (string)e.NewValue;

            if (!GetIsAttached(passwordBox))

            {

                SetIsAttached(passwordBox, true);

            }

            if ((string.IsNullOrEmpty(passwordBox.Password) && string.IsNullOrEmpty(newPassword)) ||

                passwordBox.Password == newPassword)

            {

                return;

            }

            passwordBox.PasswordChanged -= PasswordBoxHelper.PasswordBox_PasswordChanged;

            passwordBox.Password = newPassword;

            passwordBox.PasswordChanged += PasswordBoxHelper.PasswordBox_PasswordChanged;

        }

    }

}