How to update wireframe without WPF button click?

Question

I'm developing a Windows Form application with WPF User Control embedded in the WF. If I add a button and execute my userControl.DrawWireFrameCube(); My ViewPort3D get updated. I'm using Helix 3D Toolkit. But If I call my method from my MainWindowForm class it doesn't get executed and UI is not updated,but only userControl.DrawWireFrameCube(); isn't working. The other userControl.Draw3DObject(insertionPoint, points, color); method is working fine.

 private void VisualizePart(int index)
        {
            InsertionPoint insertionPoint = new InsertionPoint
            {
                X = _duplicatedListParts[index].INFO1,
                Y = _duplicatedListParts[index].INFO2,
                Z = _duplicatedListParts[index].INFO3
            };

            DetailSize points = new DetailSize
            {
                Length = _duplicatedListParts[index].LENGTH,
                Width = _duplicatedListParts[index].WIDTH,
                Thickness = _duplicatedListParts[index].THICKNESS
            };
            userControl.Dispatcher.Invoke(() =>
            {
                System.Windows.Media.Color color = System.Windows.Media.Color.FromRgb(255, 90, 0);
                userControl.Draw3DObject(insertionPoint, points, color);
                userControl.DrawWireFrameCube();
            });
        }

The difference is that in my Draw3DObject() I add items to Model3DGroup and in DrawWireFrameCube() I add items to MyViewPort3D. I'm not using XAML and I want to stay that way. Any ideas what is wrong here?

P.S I love negative vote without explanation :)