/// <summary>
        /// Create relationship if possible. Release mouse afterwards.
        /// </summary>
        /// <param name="e"></param>
        protected override void OnMouseUp(MouseButtonEventArgs e)
        {
            if (hitItem != null)
            {
                object targetElement = hitItem.SelectedData;
                if (sourceItem != null && hitItem != null && this.diagramDesigner.CreateRelationshipCommand != null)
                {
                    ViewModelRelationshipCreationInfo info = new ViewModelRelationshipCreationInfo(sourceItem.SelectedData, hitItem.SelectedData);

                    // calcualte source and target points
                    if (hitItem is FrameworkElement)
                    {
                        FrameworkElement sourceFElement = sourceConnector.DiagramItem;
                        double sourceLeft = Canvas.GetLeft(sourceFElement);
                        double sourceTop = Canvas.GetTop(sourceFElement);

                        FrameworkElement targetFElement = hitItem as FrameworkElement;
                        double targetLeft = Canvas.GetLeft(targetFElement);
                        double targetTop = Canvas.GetTop(targetFElement);
                        if (!double.IsNaN(sourceLeft) && !double.IsNaN(sourceTop) && 
                            !double.IsNaN(targetLeft) && !double.IsNaN(targetTop))
                        {
                            Point proposedTarget = e.GetPosition(this.diagramDesigner);

                            PointD proposedSourcePoint = new PointD(startPoint.X, startPoint.Y);
                            PointD proposedTargetPoint = new PointD(proposedTarget.X, proposedTarget.Y);

                            // calculate points
                            //Point sourcePointT = sourceFElement.TranslatePoint(new Point(0, 0), this.diagramDesigner);
                            //Point targetPointT = targetFElement.TranslatePoint(new Point(0, 0), this.diagramDesigner);

                            Point sourcePoint = sourceFElement.TransformToAncestor(this.diagramDesigner).Transform(new Point(0, 0));
                            Point targetPoint = targetFElement.TransformToAncestor(this.diagramDesigner).Transform(new Point(0, 0));

                            // calculate side for source
                            RectangleD sourceBounds = new RectangleD(sourcePoint.X, sourcePoint.Y, sourceFElement.Width, sourceFElement.Height);
                            info.ProposedSourcePoint = LinkShape.CalculateLocation(sourceBounds, proposedSourcePoint);

                            // calculate side for target
                            RectangleD targeteBounds = new RectangleD(targetPoint.X, targetPoint.Y, targetFElement.Width, targetFElement.Height);
                            info.ProposedTargetPoint = LinkShape.CalculateLocation(targeteBounds, proposedTargetPoint);
                        }
                    }

                    this.diagramDesigner.CreateRelationshipCommand.Execute(info);
                }
            }

            if (this.IsMouseCaptured) this.ReleaseMouseCapture();

            AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this.diagramDesigner);
            if (adornerLayer != null)
            {
                adornerLayer.Remove(this);
            }
        }
        /// <summary>
        /// Hit testing.
        /// </summary>
        /// <param name="hitPoint">Location to do a hit test at.</param>
        private void HitTesting(Point hitPoint)
        {
            DependencyObject hitObject = diagramDesigner.InputHitTest(hitPoint) as DependencyObject;
            while (hitObject != null )
            {
                if (hitObject is DiagramDesignerItem)
                {
                    hitItem = hitObject as DiagramDesignerItem;
                    if (!hitItem.IsDiagramLink)
                    {
                        if (sourceItem != null && hitItem != null && this.diagramDesigner.CreateRelationshipCommand != null)
                        {
                            object sourceData = sourceItem.SelectedData;
                            object targetData = hitItem.SelectedData;
                            if (sourceData != null && targetData != null)
                            {
                                ViewModelRelationshipCreationInfo info = new ViewModelRelationshipCreationInfo(sourceData, targetData);
                                if (info.Source != null && info.Target != null)
                                    if (this.diagramDesigner.CreateRelationshipCommand.CanExecute(info))
                                    {
                                        return;
                                    }
                            }
                        }
                    }

                    hitItem = null;
                    return;
                }

                hitObject = VisualTreeHelper.GetParent(hitObject);
            }

            hitItem = null;
        }