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VideoBrowser/Extensions/FocusExtension.cs

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+namespace VideoBrowser.Extensions
+{
+    using System.Windows;
+
+    /// <summary>
+    /// Defines the <see cref="FocusExtension" />.
+    /// </summary>
+    public static class FocusExtension
+    {
+        #region Fields
+
+        public static readonly DependencyProperty IsFocusedProperty =
+            DependencyProperty.RegisterAttached(nameof(IsFocusedProperty).Name(), typeof(bool), typeof(FocusExtension), new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnIsFocusedChanged));
+
+        public static readonly DependencyProperty TrackFocusProperty =
+            DependencyProperty.RegisterAttached(nameof(TrackFocusProperty).Name(), typeof(bool), typeof(FocusExtension), new PropertyMetadata(false, OnTrackFocusChanged));
+
+        #endregion Fields
+
+        #region Methods
+
+        /// <summary>
+        /// The GetIsFocused.
+        /// </summary>
+        /// <param name="obj">The obj<see cref="DependencyObject"/>.</param>
+        /// <returns>The <see cref="bool"/>.</returns>
+        public static bool GetIsFocused(DependencyObject obj) => (bool)obj.GetValue(IsFocusedProperty);
+
+        /// <summary>
+        /// The GetTrackFocus.
+        /// </summary>
+        /// <param name="obj">The obj<see cref="DependencyObject"/>.</param>
+        /// <returns>The <see cref="bool"/>.</returns>
+        public static bool GetTrackFocus(DependencyObject obj)
+        {
+            return (bool)obj.GetValue(TrackFocusProperty);
+        }
+
+        /// <summary>
+        /// The SetIsFocused.
+        /// </summary>
+        /// <param name="obj">The obj<see cref="DependencyObject"/>.</param>
+        /// <param name="value">The value<see cref="bool"/>.</param>
+        public static void SetIsFocused(DependencyObject obj, bool value) => obj.SetValue(IsFocusedProperty, value);
+
+        /// <summary>
+        /// The SetTrackFocus.
+        /// </summary>
+        /// <param name="obj">The obj<see cref="DependencyObject"/>.</param>
+        /// <param name="value">The value<see cref="bool"/>.</param>
+        public static void SetTrackFocus(DependencyObject obj, bool value)
+        {
+            obj.SetValue(TrackFocusProperty, value);
+        }
+
+        /// <summary>
+        /// The OnGotFocus.
+        /// </summary>
+        /// <param name="sender">The sender<see cref="object"/>.</param>
+        /// <param name="e">The e<see cref="RoutedEventArgs"/>.</param>
+        private static void OnGotFocus(object sender, RoutedEventArgs e)
+        {
+            if (!(sender is FrameworkElement element))
+            {
+                return;
+            }
+
+            if (!GetIsFocused(element))
+            {
+                SetIsFocused(element, true);
+            }
+        }
+
+        /// <summary>
+        /// The OnIsFocusedChanged.
+        /// </summary>
+        /// <param name="d">The d<see cref="DependencyObject"/>.</param>
+        /// <param name="e">The e<see cref="DependencyPropertyChangedEventArgs"/>.</param>
+        private static void OnIsFocusedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var element = (FrameworkElement)d;
+            var isFocused = (bool)e.NewValue;
+            if (isFocused)
+            {
+                element.Focus();
+            }
+        }
+
+        /// <summary>
+        /// The OnLostFocus.
+        /// </summary>
+        /// <param name="sender">The sender<see cref="object"/>.</param>
+        /// <param name="e">The e<see cref="RoutedEventArgs"/>.</param>
+        private static void OnLostFocus(object sender, RoutedEventArgs e)
+        {
+            if (!(sender is FrameworkElement element))
+            {
+                return;
+            }
+
+            if (GetIsFocused(element))
+            {
+                SetIsFocused(element, false);
+            }
+        }
+
+        /// <summary>
+        /// The OnTrackFocusChanged.
+        /// </summary>
+        /// <param name="d">The d<see cref="DependencyObject"/>.</param>
+        /// <param name="e">The e<see cref="DependencyPropertyChangedEventArgs"/>.</param>
+        private static void OnTrackFocusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            if (!(d is FrameworkElement element))
+            {
+                return;
+            }
+
+            var oldValue = (bool)e.OldValue;
+            var newValue = (bool)e.NewValue;
+
+            if (!oldValue && newValue) // If changed from false to true
+            {
+                element.GotFocus += OnGotFocus;
+                element.LostFocus += OnLostFocus;
+            }
+            else if (oldValue && !newValue) // If changed from true to false
+            {
+                element.GotFocus -= OnGotFocus;
+                element.LostFocus -= OnLostFocus;
+            }
+        }
+
+        #endregion Methods
+    }
+}