Нашел ответ:
if (!MapResourceManager1.Initialized)
                MapResourceManager1.Initialize();
            ESRI.ArcGIS.ADF.Web.DataSources.ArcGISServer.MapResourceLocal mrl = (ESRI.ArcGIS.ADF.Web.DataSources.ArcGISServer.MapResourceLocal)
                MapResourceManager1.GetResource(0);
            IMapServer ms = (IMapServer)mrl.ServerContextInfo.ServerContext.ServerObject;
            IMapServerObjects2 mso = (IMapServerObjects2)ms;
            IMap map = mso.get_Map(ms.DefaultMapName);
            IFeatureLayer2 layer = (IFeatureLayer2)map.get_Layer(2);
            IEnvelope envelope = new EnvelopeClass();
            ISpatialFilter spatialFilter = new SpatialFilterClass();
            spatialFilter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;
            IFeatureCursor fcursor = layer.Search(spatialFilter, true);
            IFeature ipfeat;
            string s = Map1.MapResourceManagerInstance.ResourceItems[0].LayerDefinitions["2"].Name;
            TreeView1.Nodes.Add(new TreeNode(s));
            for (int i = 0; i < fcursor.Fields.FieldCount; i++)
            {
                ipfeat = fcursor.NextFeature();
                TreeView1.Nodes[0].ChildNodes.Add(new TreeNode(ipfeat.get_Value(2).ToString(), ipfeat.get_Value(0).ToString()));
            }