private void ClearBufferPolygons()
        {
            // Get the collection of graphics in the graphics overlay (points and buffer polygons).
            GraphicCollection bufferGraphics = MyMapView.GraphicsOverlays["buffers"].Graphics;

            // Loop (backwards) through all graphics.
            for (int i = bufferGraphics.Count - 1; i >= 0; i--)
            {
                // If the graphic is a polygon, remove it from the overlay.
                Graphic thisGraphic = bufferGraphics[i];
                if (thisGraphic.Geometry.GeometryType == GeometryType.Polygon)
                {
                    bufferGraphics.RemoveAt(i);
                }
            }
        }