New Post: Writeablebitmap get object drawn

Is there any way to get object drawn by writeablebitmapex in windows phone 8.
In my case, i want to get eclipse which drawn previously to delete or move its. For now, i add eclipse by this code:

        int ansX1 = Convert.ToInt32(left-10);
        int ansX2 = Convert.ToInt32(left + a.ActualWidth + 10);
        int ansY1 = Convert.ToInt32(top-10);
        int ansY2 = Convert.ToInt32(top + a.ActualHeight+10);

        writeableBmp.DrawEllipse(ansX1, ansY1, ansX2, ansY2, Colors.Black);

Thanks