modified datagrid style

RowHeight, ColumnHeaderHeight, ShowSelectAllButton

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

@@ -336,5 +336,14 @@ namespace HandyControl.Controls
 
         public static bool GetCanUnselectAllWithBlankArea(DependencyObject element)
             => (bool) element.GetValue(CanUnselectAllWithBlankAreaProperty);
+
+        public static readonly DependencyProperty ShowSelectAllButtonProperty = DependencyProperty.RegisterAttached(
+            "ShowSelectAllButton", typeof(bool), typeof(DataGridAttach), new PropertyMetadata(ValueBoxes.TrueBox));
+
+        public static void SetShowSelectAllButton(DependencyObject element, bool value)
+            => element.SetValue(ShowSelectAllButtonProperty, value);
+
+        public static bool GetShowSelectAllButton(DependencyObject element)
+            => (bool) element.GetValue(ShowSelectAllButtonProperty);
     }
 }