Fixed issue with drag and drop.

1 files changed, 20 insertions, 4 deletions

diff --git a/Software/Visual_Studio/Tango.DragAndDrop/DragAndDropService.cs b/Software/Visual_Studio/Tango.DragAndDrop/DragAndDropService.cs
index 8bd5e7e0b..320891c61 100644
--- a/Software/Visual_Studio/Tango.DragAndDrop/DragAndDropService.cs
+++ b/Software/Visual_Studio/Tango.DragAndDrop/DragAndDropService.cs
@@ -500,7 +500,7 @@ namespace Tango.DragAndDrop
 
                 bool found = false;
 
-                foreach (var dropElement in _dropElements.Where(x => x != _currentDragedElement))
+                foreach (var dropElement in _dropElements.Where(x => x != null && x != _currentDragedElement))
                 {
                     if (!dropElement.IsLoaded)
                     {
@@ -532,7 +532,7 @@ namespace Tango.DragAndDrop
                     {
                         SetIsDraggableOver(dropElement, true);
 
-                        foreach (var drop in _dropElements.Where(x => x != dropElement))
+                        foreach (var drop in _dropElements.Where(x => x != null && x != dropElement))
                         {
                             SetIsDraggableOver(drop, false);
                         }
@@ -568,6 +568,14 @@ namespace Tango.DragAndDrop
         /// <param name="element">The element.</param>
         private static void RegisterDraggable(FrameworkElement element)
         {
+            foreach (var item in _dragElements.ToList())
+            {
+                if (item == null)
+                {
+                    _dragElements.Remove(item);
+                }
+            }
+
             if (!_dragElements.Contains(element))
             {
                 _dragElements.Add(element);
@@ -591,6 +599,14 @@ namespace Tango.DragAndDrop
         /// <param name="element">The element.</param>
         private static void RegisterDroppable(FrameworkElement element)
         {
+            foreach (var item in _dropElements.ToList())
+            {
+                if (item == null)
+                {
+                    _dropElements.Remove(item);
+                }
+            }
+
             if (!_dropElements.Contains(element))
             {
                 _dropElements.Add(element);
@@ -715,7 +731,7 @@ namespace Tango.DragAndDrop
             _dragTimer.Stop();
             SetIsDragging(_currentDragedElement, false);
 
-            foreach (var dropElement in _dropElements)
+            foreach (var dropElement in _dropElements.Where(x => x != null))
             {
                 SetIsDraggableOver(dropElement, false);
             }
@@ -763,7 +779,7 @@ namespace Tango.DragAndDrop
 
             FrameworkElement element = sender as FrameworkElement;
 
-            if (!_dragElements.ToList().Exists(x => x == element))
+            if (!_dragElements.Where(x => x != null).ToList().Exists(x => x == element))
             {
                 e.Handled = false;
                 return;