diff --git a/SharpMap.UI.WPF/SharpMapHost.cs b/SharpMap.UI.WPF/SharpMapHost.cs
index 5aef4080..ff956d29 100644
--- a/SharpMap.UI.WPF/SharpMapHost.cs
+++ b/SharpMap.UI.WPF/SharpMapHost.cs
@@ -403,29 +403,33 @@ private void OnMapLayerChanged(object sender, NotifyCollectionChangedEventArgs e
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
-                {
-                    var layers = sender as ObservableCollection<ILayer>;
-                    if (layers != null)
                     {
-                        foreach (var layer in layers.Where(layer => !_mapBox.Map.Layers.Contains(layer)))
+                        var layers = e.NewItems;
+                        if (layers != null)
                         {
-                            _mapBox.Map.Layers.Add(layer);
+                            foreach (var layer in layers)
+                            {
+                                var castedLayer = layer as ILayer;
+                                if (castedLayer != null && MapBox.Map.Layers.All(l => l.LayerName != castedLayer.LayerName))
+                                    MapBox.Map.Layers.Add(castedLayer);
+                            }
                         }
                     }
-                }
 
                     break;
                 case NotifyCollectionChangedAction.Remove:
-                {
-                    var layers = sender as ObservableCollection<ILayer>;
-                    if (layers != null)
                     {
-                        foreach (var layer in layers.Where(layer => _mapBox.Map.Layers.Contains(layer)))
+                        var layers = e.OldItems;
+                        if (layers != null)
                         {
-                            _mapBox.Map.Layers.Remove(layer);
+                            foreach (var layer in layers)
+                            {
+                                var castedLayer = layer as ILayer;
+                                if (castedLayer != null && MapBox.Map.Layers.Any(l => l.LayerName == castedLayer.LayerName))
+                                    MapBox.Map.Layers.Remove(castedLayer);
+                            }
                         }
                     }
-                }
 
                     break;
                 case NotifyCollectionChangedAction.Reset:
diff --git a/SharpMap.UI/Forms/MapBox.cs b/SharpMap.UI/Forms/MapBox.cs
index f5f4f3c4..5dee8884 100644
--- a/SharpMap.UI/Forms/MapBox.cs
+++ b/SharpMap.UI/Forms/MapBox.cs
@@ -2256,10 +2256,17 @@ protected override void OnMouseUp(MouseEventArgs e)
                 {
                     if (_rectangle.Width > 0 && _rectangle.Height > 0)
                     {
+                        var zoomWindowStartPoint = _dragStartPoint;
+                        var zoomWindowEndPoint = new PointF(e.X, e.Y); 
+                    
                         Coordinate lowerLeft;
                         Coordinate upperRight;
-                        GetBounds(_map.ImageToWorld(_dragStartPoint), _map.ImageToWorld(_dragEndPoint),
-                            out lowerLeft, out upperRight);
+                        GetBounds(
+                            _map.ImageToWorld(zoomWindowStartPoint), 
+                            _map.ImageToWorld(zoomWindowEndPoint),
+                            out lowerLeft, 
+                            out upperRight);
+                            
                         _dragEndPoint.X = 0;
                         _dragEndPoint.Y = 0;
 
@@ -2551,4 +2558,4 @@ static public bool PutEnhMetafileOnClipboard(IntPtr hWnd, Metafile mf)
         }
     }
 #endif
-}
\ No newline at end of file
+}