how to stop overlapping controls runtime.

Thumb addthumb = new Thumb();
                 addthumb.Height = 20;
                 addthumb.Width = lenght_[i]+25;
                 addthumb.Name = "L" + i.ToString() + "P" + i.ToString();
                 addthumb.Background = System.Windows.Media.Brushes.Orange;
                 addthumb.DragDelta += new DragDeltaEventHandler(myThumb_DragDelta);
                 Canvas.SetLeft(addthumb, position_array[balls]+25);
                 Canvas.SetTop(addthumb, 20);
                 canvas_container.Children.Add(addthumb);

private void myThumb_DragDelta(object sender, System.Windows.Controls.Primitives.DragDeltaEventArgs e)
       {
           FrameworkElement element = sender as FrameworkElement;
           Canvas.SetLeft(element, Canvas.GetLeft(element) + e.HorizontalChange);
           lbl_Heightshow.Content = element.Height;
           lbl_widthshow.Content = element.Width;
           lbl_Slub_name.Content = element.Name;
           lbl_leftposition.Content = Canvas.GetLeft(element).ToString();
           if (Canvas.GetLeft(element) == 0)
           {
               lbl_leftposition.Content = "0";
           }
           else if (Canvas.GetLeft(element) < 0)
           {
               lbl_leftposition.Content = "0";
               Canvas.SetLeft(element, 0);
           }
           else if (Canvas.GetLeft(element) + element.Width > canvas_container.ActualWidth)
           {
               lbl_leftposition.Content = (canvas_container.ActualWidth - element.Width).ToString();
               Canvas.SetLeft(element, canvas_container.ActualWidth - element.Width);
           }