Minimize to tray on Alt+F4 window close

MainWindow.xaml

@@ -16,6 +16,7 @@
         Loaded="Window_Loaded"
         Icon="Resources/icons/logo_CustomerPanel.ico"
         KeyDown="App_KeyDown"
+        Closing="Window_Closing"
         Closed="Window_Closed"
         SizeChanged="Window_SizeChanged">
     <Window.Resources>

MainWindow.xaml.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Data;
 using System.Diagnostics;
 using System.Drawing;
@@ -71,6 +72,7 @@ namespace C4IT_CustomerPanel
         private TimeSpan _lastTicketInterval;
         private TimeSpan _lastAdHocInterval;
         private TimeSpan _lastRegularInterval;
+        private bool _allowApplicationShutdown = false;
         internal DateTime lastUpdate;
 
         //private Dictionary<announcementType, List<Guid>> announcementIDCollection = new Dictionary<announcementType, List<Guid>>();
@@ -166,7 +168,7 @@ namespace C4IT_CustomerPanel
             catch (Exception E)
             {
                 LogException(E);
-                Application.Current.Shutdown();
+                RequestApplicationShutdown();
                 Environment.Exit(0);
             }
         }
@@ -1056,12 +1058,18 @@ namespace C4IT_CustomerPanel
             Application.Current.MainWindow.Topmost = false;
         }
 
+        private void RequestApplicationShutdown()
+        {
+            _allowApplicationShutdown = true;
+            Application.Current.Shutdown();
+        }
+
         private void ChangeLang(string lang)
         {
             System.Threading.Thread.CurrentThread.CurrentUICulture = new CultureInfo(lang);
 
             System.Windows.Forms.Application.Restart();
-            Application.Current.Shutdown();
+            RequestApplicationShutdown();
             notifyIcon.Dispose();
         }
 
@@ -1511,7 +1519,7 @@ namespace C4IT_CustomerPanel
             }
             else
             {
-                Application.Current.Shutdown();
+                RequestApplicationShutdown();
                 Environment.Exit(0);
             }
         }
@@ -1834,19 +1842,19 @@ namespace C4IT_CustomerPanel
             }
         }
 
-        public void Button_MouseEnter(object sender, EventArgs e)
-        {
-            try
-            {
-                if (!(sender is Button bu))
-                    return;
-
-                Color hoverColor = ConfigSettings.GetButtonHoverColor(ConfigSettings.GetBackgroundColor().Color);
-                bu.Background = new SolidColorBrush(hoverColor);
-            }
-            catch (Exception exp)
-            {
-                cLogManager.LogException(exp);
+        public void Button_MouseEnter(object sender, EventArgs e)
+        {
+            try
+            {
+                if (!(sender is Button bu))
+                    return;
+
+                Color hoverColor = ConfigSettings.GetButtonHoverColor(ConfigSettings.GetBackgroundColor().Color);
+                bu.Background = new SolidColorBrush(hoverColor);
+            }
+            catch (Exception exp)
+            {
+                cLogManager.LogException(exp);
             }
         }
 
@@ -2073,6 +2081,15 @@ namespace C4IT_CustomerPanel
             }
         }
 
+        private void Window_Closing(object sender, CancelEventArgs e)
+        {
+            if (_allowApplicationShutdown)
+                return;
+
+            e.Cancel = true;
+            HideMainForm();
+        }
+
         private void Window_SizeChanged(object sender, SizeChangedEventArgs e)
         {
             SetLocation();