private async Task CreatePictureMarkerSymbolFromUrl(GraphicsOverlay overlay)
{
// Create uri to the used image
var symbolUri = new Uri(
"http://sampleserver6.arcgisonline.com/arcgis/rest/services/Recreation/FeatureServer/0/images/e82f744ebb069bb35b234b3fea46deae");
// Create new symbol using asynchronous factory method from uri
PictureMarkerSymbol campsiteSymbol = new PictureMarkerSymbol(symbolUri);
// Optionally set the size (if not set, the size in pixels of the image will be used)
campsiteSymbol.Height = 18;
campsiteSymbol.Width = 18;
// Create location for the campsite
MapPoint campsitePoint = new MapPoint(-223560, 6552021, SpatialReferences.WebMercator);
// Create graphic with the location and symbol
Graphic campsiteGraphic = new Graphic(campsitePoint, campsiteSymbol);
// Add graphic to the graphics overlay
overlay.Graphics.Add(campsiteGraphic);
}