another little fix with grouping

Author: punker76

GongSolutions.Wpf.DragDrop/DropInfo.cs

@@ -72,6 +72,16 @@ public DropInfo(object sender, DragEventArgs e, DragInfo dragInfo)
           directlyOverItem = false;
         }
 
+        if (item == null && this.TargetGroup != null && this.TargetGroup.IsBottomLevel)
+        {
+          var itemData = this.TargetGroup.Items.FirstOrDefault();
+          if (itemData != null)
+          {
+            item = itemsControl.ItemContainerGenerator.ContainerFromItem(itemData) as UIElement;
+            directlyOverItem = false;
+          }
+        }
+
         if (item != null) {
           itemParent = ItemsControl.ItemsControlFromItemContainer(item);
 

GongSolutions.Wpf.DragDrop/Utilities/ItemsControlExtensions.cs

@@ -20,13 +20,18 @@ public static class ItemsControlExtensions
   {
     public static CollectionViewGroup FindGroup(this ItemsControl itemsControl, Point position)
     {
-      var element = itemsControl.InputHitTest(position) as DependencyObject;
+      if (itemsControl.Items.Groups == null || itemsControl.Items.Groups.Count == 0)
+      {
+        return null;
+      }
 
-      if (element != null) {
+      var element = itemsControl.InputHitTest(position) as DependencyObject;
+      if (element != null)
+      {
         var groupItem = element.GetVisualAncestor<GroupItem>();
 
         // drag after last item - get group of it
-        if (itemsControl.Items.Groups != null && groupItem == null && itemsControl.Items.Count > 0)
+        if (groupItem == null && itemsControl.Items.Count > 0)
         {
           var lastItem = itemsControl.ItemContainerGenerator.ContainerFromItem(itemsControl.Items.GetItemAt(itemsControl.Items.Count - 1)) as FrameworkElement;
           if (lastItem != null)
@@ -45,7 +50,8 @@ public static CollectionViewGroup FindGroup(this ItemsControl itemsControl, Poin
             }
           }
         }
-        if (groupItem != null) {
+        if (groupItem != null)
+        {
           return groupItem.Content as CollectionViewGroup;
         }
       }