private void Button_Click(object sender, RoutedEventArgs e) { WebClient client = new WebClient(); client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted); string soeURL = "http://10.25.3.130/ArcGIS/rest/services/Goa/SOE_RnD/MapServer/exts/TestRESTSOE/sampleOperation?LayerName=DT&FieldName=DtCode&f=pjson"; client.OpenReadAsync(new Uri(soeURL)); }