Added PasswordBoxHelper to provide possibility to bind password in MVVM

Author: dbeuchler

Directory.build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <LangVersion>8.0</LangVersion>
+    <LangVersion>9.0</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup>

src/Moryx.WpfToolkit/Moryx.WpfToolkit.csproj.DotSettings

@@ -56,6 +56,7 @@
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=ListView/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=multiprogressbar/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=localization/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=passwordbox/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=ProgressBar/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=propertychanged/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=radiobutton/@EntryIndexedValue">True</s:Boolean>

src/Moryx.WpfToolkit/PasswordBox/PasswordBoxHelper.cs

@@ -0,0 +1,104 @@
+using System.Windows;
+using System.Windows.Controls;
+
+namespace Moryx.WpfToolkit
+{
+    /// <summary>
+    /// Helper class for the password box to bind the password
+    /// </summary>
+    public static class PasswordBoxHelper
+    {
+        /// <summary>
+        /// Attached property for the bound password
+        /// </summary>
+        public static readonly DependencyProperty BoundPassword =
+            DependencyProperty.RegisterAttached("BoundPassword", typeof(string), typeof(PasswordBoxHelper), new PropertyMetadata(string.Empty, OnBoundPasswordChanged));
+
+        /// <summary>
+        /// Attached property for the bind password
+        /// </summary>
+        public static readonly DependencyProperty BindPassword = DependencyProperty.RegisterAttached(
+            "BindPassword", typeof(bool), typeof(PasswordBoxHelper), new PropertyMetadata(false, OnBindPasswordChanged));
+
+        private static readonly DependencyProperty UpdatingPassword =
+            DependencyProperty.RegisterAttached("UpdatingPassword", typeof(bool), typeof(PasswordBoxHelper), new PropertyMetadata(false));
+
+        /// <summary>
+        /// Gets the <see cref="BindPassword"/> value
+        /// </summary>
+        public static bool GetBindPassword(DependencyObject dp) =>
+            (bool)dp.GetValue(BindPassword);
+
+        /// <summary>
+        /// Sets the <see cref="BindPassword"/> value
+        /// </summary>
+        public static void SetBindPassword(DependencyObject dp, bool value) =>
+            dp.SetValue(BindPassword, value);
+
+        /// <summary>
+        /// Gets the <see cref="BoundPassword"/> value
+        /// </summary>
+        public static string GetBoundPassword(DependencyObject dp) =>
+            (string)dp.GetValue(BoundPassword);
+
+        /// <summary>
+        /// Sets the <see cref="BoundPassword"/> value
+        /// </summary>
+        public static void SetBoundPassword(DependencyObject dp, string value) =>
+            dp.SetValue(BoundPassword, value);
+
+        private static bool GetUpdatingPassword(DependencyObject dp) =>
+            (bool)dp.GetValue(UpdatingPassword);
+
+        private static void SetUpdatingPassword(DependencyObject dp, bool value) =>
+            dp.SetValue(UpdatingPassword, value);
+
+        private static void OnBoundPasswordChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var box = d as PasswordBox;
+
+            // only handle this event when the property is attached to a PasswordBox
+            // and when the BindPassword attached property has been set to true
+            if (d == null || !GetBindPassword(d))
+                return;
+
+            // avoid recursive updating by ignoring the box's changed event
+            box.PasswordChanged -= HandlePasswordChanged;
+
+            var newPassword = (string)e.NewValue;
+
+            if (!GetUpdatingPassword(box))
+                box.Password = newPassword;
+
+            box.PasswordChanged += HandlePasswordChanged;
+        }
+
+        private static void OnBindPasswordChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
+        {
+            // When the BindPassword attached property is set on a PasswordBox,
+            // start listening to its PasswordChanged event
+            if (dp is not PasswordBox box)
+                return;
+
+            var wasBound = (bool)e.OldValue;
+            var needToBind = (bool)e.NewValue;
+
+            if (wasBound)
+                box.PasswordChanged -= HandlePasswordChanged;
+
+            if (needToBind)
+                box.PasswordChanged += HandlePasswordChanged;
+        }
+
+        private static void HandlePasswordChanged(object sender, RoutedEventArgs e)
+        {
+            var box = sender as PasswordBox;
+
+            // set a flag to indicate that we're updating the password
+            SetUpdatingPassword(box, true);
+            // push the new password into the BoundPassword property
+            SetBoundPassword(box, box.Password);
+            SetUpdatingPassword(box, false);
+        }
+    }
+}