How to get graphic attribute values

Question

Hi -
I thought I knew this but I guess I don't. Given a graphic with attributes, how do you obtain the value of a specific attribute key?
I have the following:  foreach (Graphic g in featureSet.Features)
                {
     //Graphic gr = featureSet.Features[0];
                    g.Symbol = LayoutRoot.Resources["LinesSymbol"] as LineSymbol;
                    graphicsLayer.Graphics.Add(g);

ID = g.Attributes["PAGsde.DBO.TrafficCountNetwork.OBJECTID"] as string;
     
     // How to get at graphic attributes
     //foreach (var a in g.Attributes)
     //{
     //    MessageBox.Show(a.Key + ":   " + a.Value);
     //}
                }

The loop which is commented out reveals that the key "PAGsde.DBO.TrafficCountNetwork.OBJECTID" is a valid key with a value but ID always comes up null. How can I assign the key value to the variable?
Thanks

DonFreeman · Answer

Your feature layer doesn't allow querying on related data.

If you look at this working sample : http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Petroleum/KSPetro/MapServer/0  you'll notice the 2 relationships to 'Tops' and 'Fields', and the 'Query Related Records' URL at the botton of the page.

Your service has not these capabilities.

To allow querying on related data, you must defined a Relationship in your geodatabase and your published map document must contain the 2 layers or tables involved in the Relationship class.

Thank you, thank you, thank you. After thinking about it more I suspected the problem was with the service. We had all joins and no relates. That simple suggestion took care of it. Problem solved!

DominiqueBroux · Answer

Your feature layer doesn't allow querying on related data.

If you look at this working sample : http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Petroleum/KSPetro/MapServer/0  you'll notice the 2 relationships to 'Tops' and 'Fields', and the 'Query Related Records' URL at the botton of the page.

Your service has not these capabilities.

To allow querying on related data, you must defined a Relationship in your geodatabase and your published map document must contain the 2 layers or tables involved in the Relationship class.

DonFreeman · Answer

Thanks Dom. That solved the problem. I didn't realize there was a difference between the two syntaxes. However the bad news is I was chasing the wrong rabbit. I am trying to fix some code someone else wrote and frankly I don't understand it all that well.  The actual problem has to do with a relationship query. This code :
Int32 MyVar = Convert.ToInt32(g.Attributes[SelectedRoadsTreeView.Tag as string]);

RelationshipParameter relationshipParameters = new RelationshipParameter()
{
  ObjectIds = new int[] { Convert.ToInt32(g.Attributes[SelectedRoadsTreeView.Tag as string]) },
  OutFields = new string[] { "loc_id, count_id, _year, adt" },
  RelationshipId = 0,
  OutSpatialReference = Map.SpatialReference
};
queryTask.ExecuteRelationshipQueryAsync(relationshipParameters);

fails when it runs with a message that there are missing or invalid parameters. The first line verifies that there is a valid objectid (739 in my case). The service that it is accessing is http://gismaps.pagnet.org/arcgis/rest/services/tempTrafficcounts/MapServer/0.

Can you suggest what might be wrong? The problem may be with the service since the original was destroyed and we tried to recreate it. Perhaps I need something structured differently there? Thanks for any help.