optimized performance

src/Shared/HandyControl_Shared/Controls/Base/SelectableItem.cs

@@ -67,7 +67,7 @@ namespace HandyControl.Controls
         public bool IsSelected
         {
             get => (bool)GetValue(IsSelectedProperty);
-            set => SetValue(IsSelectedProperty, value);
+            set => SetValue(IsSelectedProperty, ValueBoxes.BooleanBox(value));
         }
 
         public static readonly DependencyProperty SelfManageProperty = DependencyProperty.Register(
@@ -76,7 +76,7 @@ namespace HandyControl.Controls
         public bool SelfManage
         {
             get => (bool) GetValue(SelfManageProperty);
-            set => SetValue(SelfManageProperty, value);
+            set => SetValue(SelfManageProperty, ValueBoxes.BooleanBox(value));
         }
 
         public static readonly DependencyProperty CanDeselectProperty = DependencyProperty.Register(
@@ -85,7 +85,7 @@ namespace HandyControl.Controls
         public bool CanDeselect
         {
             get => (bool) GetValue(CanDeselectProperty);
-            set => SetValue(CanDeselectProperty, value);
+            set => SetValue(CanDeselectProperty, ValueBoxes.BooleanBox(value));
         }
 
         public static readonly RoutedEvent SelectedEvent =

src/Shared/HandyControl_Shared/Controls/Base/SimpleItemsControl.cs

@@ -38,7 +38,7 @@ namespace HandyControl.Controls
             {
                 if (e.NewItems != null && e.NewItems.Count > 0)
                 {
-                    SetValue(HasItemsPropertyKey, true);
+                    SetValue(HasItemsPropertyKey, ValueBoxes.TrueBox);
                 }
                 OnItemsChanged(s, e);
             };