Some problem in sample DynamicLayerEditGeometry

[sergeysergey1]

url = string.Format("{0}/{1}", url, id);
                    table = await ServiceFeatureTable.OpenAsync(new Uri(url), null, MyMapView.SpatialReference);
                }
                // Retrieves feature identified by ID and updates its geometry 
                // using GeometryEngine to correct ring orientation.
                var feature = await table.QueryAsync(featureID);
                var geometry = await MyMapView.Editor.EditGeometryAsync(feature.Geometry);

feature = null, so i have exception. I try it on windows 2008 server,notebook windows 8.1, that i had not error. But on my compute i had error, now i reinstall windows 8, but i have error too.