I'm not sure I understand your question.
Geometry Service do not have features and therefore do not have a concept of saving features.
Maybe there's confusion here. You can look at the following documentation: http://help.arcgis.com/en/arcgisserver/10.0/help/arcgis_server_dotnet_help/index.html#//009300000027...
ESRI.ArcGIS.Client.Geometry.Polygon insertPolygon = new ESRI.ArcGIS.Client.Geometry.Polygon(); //create a new polygon insertPolygon.Rings.Add(pPointCollection); //copy all points of the drawn polygon to the newly created polygon ESRI.ArcGIS.Client.FeatureLayer myFeatureLayer = MyMap.Layers["MyFeatureLayer"] as FeatureLayer; //declear a featurelayer ESRI.ArcGIS.Client.Graphic insertGraphic = new ESRI.ArcGIS.Client.Graphic() //Create a Graphic object { Geometry = insertPolygon, //assign the newly polygon to the graphic's geometry property Attributes = myFeatureLayer.LayerInfo //assign values to the graphic's attributes, which can be known from the feature layer's LayerInfo attribute }; myFeatureLayer.Graphics.Add(insertGraphic); //add the graphic object to the Graphics collection of the feature layer
Attributes = myFeatureLayer.LayerInfo
graphic.Attributes["fieldname"] = value;Also the types do not match. Attributes is of type IDictionary<string, object> http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.Graphic~At... and LayerInfo is of type FeatureLayerInfo http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.FeatureSer....
foreach (var field in Layer.LayerInfo.Fields) { // check field properties here (Editable / Nullable/ Type) //so you can decide what value to give each attribute }