protected override void OnRender(DrawingContext drawingContext)
{
base.OnRender(drawingContext);
graph.UpdateTransform(ActualWidth * (1 - 2 * InnerMargin), ActualHeight * (1 - 2 * InnerMargin),
ActualWidth * InnerMargin, ActualHeight * InnerMargin);
drawingContext.DrawDrawing(graph.Drawing);
}