ArcGIS Pro 3.3 API Reference Guide
ArcGIS.Core.Data.Knowledge Namespace / KnowledgeGraphRow Class / Item Property
Example

In This Topic
    Item Property (KnowledgeGraphRow)
    In This Topic
    Gets the value in the graph row specified by the index. This indexer must be called on the MCT. Use QueuedTask.Run.
    Syntax
    public object this[ 
       int index
    ]; {get;}
    Public ReadOnly Default Property Item( _
       ByVal index As Integer _
    ) As Object

    Parameters

    index

    Property Value

    The value at the specified index.
    Exceptions
    ExceptionDescription
    This method or property must be called within the lambda passed to QueuedTask.Run.
    Remarks
    The value can be a primitive value (number, string, date, etc), geometry, or other KnowledgeGraphValue depending on the nature of the original query.
    Example
    Submit a Graph Query
    //On the QueuedTask...
    //and assuming you have established a connection to a knowledge graph
    //...
    //Construct an openCypher query - return the first 10 entities (whatever
    //they are...)
    var query = "MATCH (n) RETURN n LIMIT 10";//default limit is 100 if not specified
    //other examples...
    //query = "MATCH (a:Person) RETURN [a.name, a.age] ORDER BY a.age DESC LIMIT 50";
    //query = "MATCH (b:Person) RETURN { Xperson: { Xname: b.name, Xage: b.age } } ORDER BY b.name DESC";
    //query = "MATCH p = (c:Person)-[:HasCar]-() RETURN p ORDER BY c.name DESC";
    
    //Create a query filter
    //Note: OutputSpatialReference is currently ignored
    var kg_qf = new KnowledgeGraphQueryFilter()
    {
      QueryText = query
    };
    //Optionally - u can choose to include provenance in the results
    //(_if_ the KG has provenance - otherwise the query will fail)
    if (includeProvenanceIfPresent)
    {
      //see "Get Whether KG Supports Provenance" snippet
      if (KnowledgeGraphSupportsProvenance(kg))
      {
        //Only include if the KG has provenance
        kg_qf.ProvenanceBehavior = 
          KnowledgeGraphProvenanceBehavior.Include;//default is exclude
      }
    }
    //submit the query - returns a KnowledgeGraphCursor
    using (var kg_rc = kg.SubmitQuery(kg_qf))
    {
      //wait for rows to be returned from the server
      //note the "await"...
      while (await kg_rc.WaitForRowsAsync())
      {
        //Rows have been retrieved - process this "batch"...
        while (kg_rc.MoveNext())
        {
          //Get the current KnowledgeGraphRow
          using (var graph_row = kg_rc.Current)
          {
            //Graph row is an array, process all returned values...
            var val_count = (int)graph_row.GetCount();
            for (int i = 0; i < val_count; i++)
            {
              var retval = graph_row[i];
              //Process row value (note: recursive)
              //See "Process a KnowledgeGraphRow Value" snippet
              ProcessKnowledgeGraphRowValue(retval);
            }
          }
        }
      }//WaitForRowsAsync
    }//SubmitQuery
    Submit a Text Search
    //On the QueuedTask...
    //and assuming you have established a connection to a knowledge graph
    //...
    //Construct a KG search filter. Search text uses Apache Lucene Query Parser
    //syntax - https://lucene.apache.org/core/2_9_4/queryparsersyntax.html
    var kg_sf = new KnowledgeGraphSearchFilter()
    {
      SearchTarget = KnowledgeGraphNamedTypeCategory.Entity,
      SearchText = "Acme Electric Co.",
      ReturnSearchContext = true,
      MaxRowCount = 10 //Default is 100 if not specified
    };
    
    //submit the search - returns a KnowledgeGraphCursor
    var e = 0;
    using (var kg_rc = kg.SubmitSearch(kg_sf))
    {
      //wait for rows to be returned from the server
      //note the "await"...
      while (await kg_rc.WaitForRowsAsync())
      {
        //Rows have been retrieved - process this "batch"...
        while (kg_rc.MoveNext())
        {
          //Get the current KnowledgeGraphRow
          using (var graph_row = kg_rc.Current)
          {
            //We are returning entities from this search
            var entity = graph_row[0] as KnowledgeGraphEntityValue;
            var entity_type = entity.GetTypeName();
            var record = new List<string>();
            //discover keys(aka "fields") dynamically via GetKeys
            foreach (var prop_name in entity.GetKeys())
            {
              var obj_val = entity[prop_name] ?? "null";
              record.Add(obj_val.ToString());
            }
            System.Diagnostics.Debug.WriteLine(
              $"{entity_type}[{e++}] " + string.Join(", ", record));
            //or use "Process a KnowledgeGraphRow Value" snippet
            //ProcessKnowledgeGraphRowValue(entity);
          }
        }
      }//WaitForRowsAsync
    }//SubmitSearch
    Process a KnowledgeGraphRow Value
    //Base class for entities and relationships
    //(including documents and provenance)
    public void ProcessGraphNamedObjectValue(
      KnowledgeGraphNamedObjectValue kg_named_obj_val)
    {
      if (kg_named_obj_val is KnowledgeGraphEntityValue kg_entity)
      {
        var label = kg_entity.GetLabel();
        //TODO - use label
      }
      else if (kg_named_obj_val is KnowledgeGraphRelationshipValue kg_rel)
      {
        var has_entity_ids = kg_rel.GetHasRelatedEntityIDs();
        if (kg_rel.GetHasRelatedEntityIDs())
        {
          var origin_id = kg_rel.GetOriginID();
          var dest_id = kg_rel.GetDestinationID();
          //TODO - use ids
        }
      }
      var id = kg_named_obj_val.GetID();
      var oid = kg_named_obj_val.GetObjectID();
      //Note: Typename corresponds to the name of the feature class or table
      //in the relational gdb model -and- to the name of the KnowledgeGraphNamedObjectType
      //in the knowledge graph data model
      var type_name = kg_named_obj_val.GetTypeName();
      //TODO use id, object id, etc.
    }
    
    //Object values include entities, relationships, and anonymous objects
    public void ProcessGraphObjectValue(KnowledgeGraphObjectValue kg_obj_val)
    {
      switch (kg_obj_val)
      {
        case KnowledgeGraphEntityValue kg_entity:
          ProcessGraphNamedObjectValue(kg_entity);
          break;
        case KnowledgeGraphRelationshipValue kg_rel:
          ProcessGraphNamedObjectValue(kg_rel);
          break;
        default:
          //Anonymous objects
          break;
      }
      //graph object values have a set of properties (equivalent
      //to a collection of key/value pairs)
      var keys = kg_obj_val.GetKeys();
      foreach (var key in keys)
        ProcessKnowledgeGraphRowValue(kg_obj_val[key]);//Recurse
    }
    
    //Process a KnowledgeGraphValue from a query or search
    public void ProcessGraphValue(KnowledgeGraphValue kg_val)
    {
      switch (kg_val)
      {
        case KnowledgeGraphPrimitiveValue kg_prim:
          //KnowledgeGraphPrimitiveValue not currently used in
          //query and search 
          ProcessKnowledgeGraphRowValue(kg_prim.GetValue());//Recurse
          return;
        case KnowledgeGraphArrayValue kg_array:
          var count = kg_array.GetSize();
          //Recursively process each value in the array
          for (ulong i = 0; i < count; i++)
            ProcessKnowledgeGraphRowValue(kg_array[i]);//Recurse
          return;
        case KnowledgeGraphPathValue kg_path:
          //Entities
          var entity_count = kg_path.GetEntityCount();
          //Recursively process each entity value in the path
          for (ulong i = 0; i < entity_count; i++)
            ProcessGraphObjectValue(kg_path.GetEntity(i));//Recurse
    
          //Recursively process each relationship value in the path
          var relate_count = kg_path.GetRelationshipCount();
          for (ulong i = 0; i < relate_count; i++)
            ProcessGraphObjectValue(kg_path.GetRelationship(i));//Recurse
          return;
        case KnowledgeGraphObjectValue kg_object:
          ProcessGraphObjectValue(kg_object);//Recurse
          return;
        default:
          var type_string = kg_val.GetType().ToString();
          System.Diagnostics.Debug.WriteLine(
            $"Unknown: '{type_string}'");
          return;
      }
    }
    
    //Process each value from the KnowledgeGraphRow array
    public void ProcessKnowledgeGraphRowValue(object value)
    {
      switch (value)
      {
        //Graph value?
        case KnowledgeGraphValue kg_val:
          var kg_type = kg_val.KnowledgeGraphValueType.ToString();
          System.Diagnostics.Debug.WriteLine(
            $"KnowledgeGraphValue: '{kg_type}'");
          ProcessGraphValue(kg_val);//Recurse
          return;
        //Primitive types...add additional logic as needed
        case System.DBNull dbn:
          System.Diagnostics.Debug.WriteLine("DBNull.Value");
          return;
        case string str:
          System.Diagnostics.Debug.WriteLine($"'{str}' (string)");
          return;
        case long l_val:
          System.Diagnostics.Debug.WriteLine($"{l_val} (long)");
          return;
        case int i_val:
          System.Diagnostics.Debug.WriteLine($"{i_val} (int)");
          return;
        case short s_val:
          System.Diagnostics.Debug.WriteLine($"{s_val} (short)");
          return;
        case double d_val:
          System.Diagnostics.Debug.WriteLine($"{d_val} (double)");
          return;
        case float f_val:
          System.Diagnostics.Debug.WriteLine($"{f_val} (float)");
          return;
        case DateTime dt_val:
          System.Diagnostics.Debug.WriteLine($"{dt_val} (DateTime)");
          return;
        case DateOnly dt_only_val:
          System.Diagnostics.Debug.WriteLine($"{dt_only_val} (DateOnly)");
          return;
        case TimeOnly tm_only_val:
          System.Diagnostics.Debug.WriteLine($"{tm_only_val} (TimeOnly)");
          return;
        case DateTimeOffset dt_tm_offset_val:
          System.Diagnostics.Debug.WriteLine(
            $"{dt_tm_offset_val} (DateTimeOffset)");
          return;
        case System.Guid guid_val:
          var guid_string = guid_val.ToString("B");
          System.Diagnostics.Debug.WriteLine($"'{guid_string}' (Guid)");
          return;
        case Geometry geom_val:
          var geom_type = geom_val.GeometryType.ToString();
          var is_empty = geom_val.IsEmpty;
          var wkid = geom_val.SpatialReference?.Wkid ?? 0;
          System.Diagnostics.Debug.WriteLine(
            $"geometry: {geom_type}, empty: {is_empty}, sr_wkid {wkid} (shape)");
          return;
        default:
          //Blob? Others?
          var type_str = value.GetType().ToString();
          System.Diagnostics.Debug.WriteLine($"Primitive: {type_str}");
          return;
      }
    }
    
    // ...submit query or search
    //using (var kg_rc = kg.SubmitQuery(kg_qf)) {
    //using (var kg_rc = kg.SubmitSearch(kg_sf)) {
    //  ...wait for rows ...
    //  while (await kg_rc.WaitForRowsAsync()) {
    //   ...rows have been retrieved
    //   while (kg_rc.MoveNext()) {
    //     ...get the current KnowledgeGraphRow
    //     using (var graph_row = kg_rc.Current) {
    //        var val_count = (int)graph_row.GetCount();
    //        for (int i = 0; i<val_count; i++)
    //           ProcessKnowledgeGraphRowValue(graph_row[i]);
    
    Requirements

    Target Platforms: Windows 11, Windows 10

    ArcGIS Pro version: 3.2 or higher.
    See Also