FeatureSet fs = new FeatureSet();
fs.ObjectIdFieldName = "ID";
//fs.GlobalIdFieldName = "ID";
//fs.SpatialReference = new SpatialReference(4326);
fs.Features.Add(new ESRI.ArcGIS.Client.Graphic() { Attributes = { { "ID", "1" } } });
Console.WriteLine(fs.ToJson());
FeatureSet fs = new FeatureSet(); fs.ObjectIdFieldName = "ID"; Console.WriteLine(fs.ToJson());