Thank you Stoyan, I will try that ..
. is there a way to place link labels at a desired proper position... please see the image that I will send through email. somehow  the link labels don’t start at the position that we would like to have it..

Hi Stoyan,
I implemented this code.. however I get this Compile time error..
Error2'MindFusion.Diagramming.Silverlight.Utilities' does not contain a definition for 'Mid'
am I missing some dll or its version... when do you guys plan to release the next version of Diagramlitedll?

Hi Stoyan, I implemented everything you said.. And something’s work great but not all..
1) When I create a link that was saved earlier in the database.. I create and set the text block margins like this..


List<Point> points = link2.ControlPoints;
                       Point midPoint = new Point(
                           (points[0].X + points[points.Count - 1].X) / 2,
                           ((points[0].Y + points[points.Count - 1].Y) / 2));

                       Rect bounds = link2.GetBounds();

                       link2.TextBlock.Margin = new Thickness(midPoint.X - bounds.X - link2.TextBlock.ActualWidth / 2, midPoint.Y - bounds.Y - link2.TextBlock.ActualHeight, 0, 0);

And this works great..

After I draw all the nodes and links I go to the database again and make a call to get the users last saved geometry (if available). This geometry stores the control points and label position. I then set those settings like this..
  RouteLabelLocation lableLocation = routeGeometry.labelLocation;
                           if (lableLocation.xCoordinate != 0 && lableLocation.yCoordinate != 0)
                           {

                               link.TextBlock.Margin = new Thickness(lableLocation.xCoordinate, lableLocation.yCoordinate, 0, 0);
                                                         }
                           link.UpdateFromPoints();

Somehow the user set label positions are not reflected.

2) When the user drags the labels there is a gap between the mouse cursor and the label. Like a huge gap sometimes 100 pixel differences. This started only after I started setting the margins.. What code changes should I do to make the label follow the mouse co-ordinates? 

Thanks Stoyan.. I have implemented this.. it seems to work ok.. There are a few pixel difference between what I save and retrieve.. I am not sure if I am doing the right thing.. I am saving the Top and Y co-ordinate and Left for X co-ordinate.

when will you release the production version of the dll whereby we will be able to double click the link label and Raise the routes double click event handler?

In version 1.8 later this month.

OK, I implemented the beta control and now I have an issue when I multi-select the routes. I am setting the select property within the control and I get a null pointer exception.

       public bool IsSelected
       {
           get { return isSelected; }
           set
           {
               isSelected = value;
               if (value)
               {
                   Selected = true;
                   TextBlock.FontWeight = FontWeights.ExtraBold;
               }
               else
               {
                   Selected = false;
                   TextBlock.FontWeight = FontWeights.Normal;
               }
           }
       }

System.NullReferenceException was unhandled by user code
  Message="Object reference not set to an instance of an object."
  StackTrace:
      at MindFusion.Diagramming.Silverlight.Selection.RemoveItem(DiagramItem item)
      at MindFusion.Diagramming.Silverlight.DiagramItem.set_Selected(Boolean value)
      at ProcessDesigner.ViewModel.CustomDiagramLink.set_IsSelected(Boolean value)
      at ProcessDesigner.MainPage.diagram_LinkSelected(Object sender, LinkEventArgs e)
      at MindFusion.Diagramming.Silverlight.Diagram.OnLinkSelected(LinkEventArgs e)
      at MindFusion.Diagramming.Silverlight.Diagram.x687b9b7bc932d66f(DiagramItem xccb63ca5f63dc470)
      at MindFusion.Diagramming.Silverlight.DiagramItem.x5db081b43af662f4(Boolean x8f9d3ffcb9383cde)
      at MindFusion.Diagramming.Silverlight.Selection.xc72e48b5cfcebb45(DiagramItem xccb63ca5f63dc470)
      at MindFusion.Diagramming.Silverlight.Selection.x5de01b52457c5b58(Rect x26545669838eb36e)
      at MindFusion.Diagramming.Silverlight.Selection.EndDrag(InteractionState ist)
      at MindFusion.Diagramming.Silverlight.InteractionState.Commit(Point currentPoint)
      at MindFusion.Diagramming.Silverlight.BehaviorBase.OnMouseUp(MouseButtonEventArgs e)
      at MindFusion.Diagramming.Silverlight.Diagram.x66c89b500bffc63d(Object xe0292b9ed559da7d, MouseButtonEventArgs xfbf34718e704c6bc)
      at MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
      at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)
  InnerException:


Don

OK, yea that was it. I was setting selected in mouse down of the custom links. Can I take a node out of the hit test? I.E. make it pass through.

Note: I tried setting the IsHitTestVisable property of the swim lanes but it still doesn't pass the double click to the link underneath.