Add attached property "WindowAttach.HiddenInsteadClose".

Add property "ShowMainWindowOnClick" for "NotifyIcon".

src/Shared/HandyControl_Shared/Controls/Attach/WindowAttach.cs

@@ -109,6 +109,42 @@ namespace HandyControl.Controls
             => element.SetValue(ShowInTaskManagerProperty, ValueBoxes.BooleanBox(value));
 
         public static bool GetShowInTaskManager(DependencyObject element)
-            => (bool) element.GetValue(ShowInTaskManagerProperty);
+            => (bool)element.GetValue(ShowInTaskManagerProperty);
+
+        /// <summary>
+        /// 隐藏窗口而不是关闭，在使用 <see cref="NotifyIcon"/> 时很有用，这时点击主窗口的关闭按钮通常是隐藏窗口而不是退出程序
+        /// </summary>
+        public static readonly DependencyProperty HiddenInsteadCloseProperty =
+            DependencyProperty.RegisterAttached("HiddenInsteadClose", typeof(bool), typeof(WindowAttach), new PropertyMetadata(false, HiddenInsteadClosePropertyChanged));
+
+        public static bool GetHiddenInsteadClose(DependencyObject obj)
+        {
+            return (bool)obj.GetValue(HiddenInsteadCloseProperty);
+        }
+
+        public static void SetHiddenInsteadClose(DependencyObject obj, bool value)
+        {
+            obj.SetValue(HiddenInsteadCloseProperty, value);
+        }
+
+        private static void HiddenInsteadClosePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            if (d is System.Windows.Window window && e.NewValue is bool enabled)
+            {
+                if (enabled)
+                    window.Closing += Window_Closing;
+                else
+                    window.Closing -= Window_Closing;
+            }
+        }
+
+        private static void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
+        {
+            if (sender is System.Windows.Window window)
+            {
+                window.Hide();
+                e.Cancel = true;
+            }
+        }
     }
 }

src/Shared/HandyControl_Shared/Controls/Other/NotifyIcon.cs

@@ -387,6 +387,38 @@ namespace HandyControl.Controls
             }
         }
 
+        public static readonly DependencyProperty ShowMainWindowOnClickProperty =
+            DependencyProperty.RegisterAttached("ShowMainWindowOnClick", typeof(bool), typeof(NotifyIcon),
+                                                new PropertyMetadata(false, OnShowMainWindowOnClickChanged));
+
+        private static void OnShowMainWindowOnClickChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            if (d is NotifyIcon notifyIcon && e.NewValue is bool enabled)
+            {
+                if (enabled)
+                    notifyIcon.Click += NotifyIcon_Click;
+                else
+                    notifyIcon.Click -= NotifyIcon_Click;
+            }
+        }
+
+        private static void NotifyIcon_Click(object sender, RoutedEventArgs e)
+        {
+            if (sender is NotifyIcon)
+            {
+                Application.Current.MainWindow.Show();
+                Application.Current.MainWindow.Activate();
+            }
+        }
+
+        /// <summary>
+        /// 设置或获取点击托盘图标时是否显示主窗口
+        /// </summary>
+        public bool ShowMainWindowOnClick {
+            get => (bool)GetValue(ShowMainWindowOnClickProperty);
+            set => SetValue(ShowMainWindowOnClickProperty, value);
+        }
+
         //referenced from http://www.cnblogs.com/sczmzx/p/5158127.html
         private IntPtr FindTrayToolbarWindow()
         {