add IgnoreAltF4 Attached Property

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

@@ -37,5 +37,37 @@ namespace HandyControl.Controls
                 System.Windows.Window.GetWindow(obj)?.DragMove();
             }
         }
+
+        public static readonly DependencyProperty IgnoreAltF4Property = DependencyProperty.RegisterAttached(
+            "IgnoreAltF4", typeof(bool), typeof(WindowAttach), new PropertyMetadata(ValueBoxes.FalseBox, OnIgnoreAltF4Changed));
+
+        private static void OnIgnoreAltF4Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            if (d is System.Windows.Window window)
+            {
+                if ((bool)e.NewValue)
+                {
+                    window.PreviewKeyDown += Window_PreviewKeyDown;
+                }
+                else
+                {
+                    window.PreviewKeyDown -= Window_PreviewKeyDown;
+                }
+            }
+        }
+
+        private static void Window_PreviewKeyDown(object sender, KeyEventArgs e)
+        {
+            if (e.Key == Key.System && e.SystemKey == Key.F4)
+            {
+                e.Handled = true;
+            }
+        }
+
+        public static void SetIgnoreAltF4(DependencyObject element, bool value)
+            => element.SetValue(IgnoreAltF4Property, value);
+
+        public static bool GetIgnoreAltF4(DependencyObject element)
+            => (bool) element.GetValue(IgnoreAltF4Property);
     }
 }

src/Shared/HandyControl_Shared/Controls/Input/NumericUpDown.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Windows;
 using System.Windows.Controls;
-using System.Windows.Documents;
 using System.Windows.Input;
 using HandyControl.Data;
 using HandyControl.Interactivity;