public sealed class KnowledgeGraph : ArcGIS.Core.Data.Datastore, System.IDisposable  

{
  await QueuedTask.Run(() =>
  {
    //Create a connection properties
    var kg_props =
        new KnowledgeGraphConnectionProperties(new Uri(url));
    try
    {
      //Open a connection
      using (var kg = new KnowledgeGraph(kg_props))
      {
        //TODO...use the KnowledgeGraph
      }
    }
    catch (GeodatabaseNotFoundOrOpenedException ex)
    {
      System.Diagnostics.Debug.WriteLine(ex.ToString());
    }
  });
}

{
  await QueuedTask.Run(() =>
  {
    //Starting at 3.7, users can connect to a _file_ knowledge graph
    //The extension for a file kg is ".knowledgegraph"
    // Any path you want
    string kgPath = @"C:\Data\KG\Filebased_KG";
    string kgFileName = @"Test_File_KG.knowledgegraph";

    var kg_full_path = System.IO.Path.Combine(kgPath, kgFileName);

    var kg_props = new KnowledgeGraphConnectionProperties(new Uri(kg_full_path));
    try
    {
      //Open a connection
      using (var kg = new KnowledgeGraph(kg_props))
      {
        //TODO...use the File KnowledgeGraph
        var i = 0;
        //Get the featureclass definitions from the KG datastore
        var fc_defs = kg.GetDefinitions<FeatureClassDefinition>();
        //For each feature class definition, get the corresponding
        //feature class. Note: The name of the feature class will match 
        //the name of its corresponding KnowledgeGraph named object type
        //in the KnowledgeGraph graph data model
        foreach (var fc_def in fc_defs)
        {
          var fc_name = fc_def.GetName();
          System.Diagnostics.Debug.WriteLine($"FeatureClass[{i++}] {fc_name}");
        }
      }
    }
    catch (GeodatabaseNotFoundOrOpenedException ex)
    {
      System.Diagnostics.Debug.WriteLine(ex.ToString());
    }
  });
}

{
  //var kgLayer = MapView.Active.Map.GetLayersAsFlattenedList()
  //			.OfType<KnowledgeGraphLayer>().FirstOrDefault();

  await QueuedTask.Run(() =>
  {
    // use the layer directly
    KnowledgeGraph datastore = kgLayer.GetDatastore();

    // or you can use any of the sub items since
    //KnowledgeGraphLayer is a composite layer - get the first 
    // child feature layer or standalone table
    var featlayer = kgLayer?.GetLayersAsFlattenedList()?
                    .OfType<FeatureLayer>()?.FirstOrDefault();
    KnowledgeGraph kg = null;
    if (featlayer != null)
    {
      using (var fc = featlayer.GetFeatureClass())
        kg = fc.GetDatastore() as KnowledgeGraph;
      //TODO use KnowledgeGraph
    }
    else
    {
      //try standalone table
      var stbl = kgLayer?.GetStandaloneTablesAsFlattenedList()?
                      .FirstOrDefault();
      if (stbl != null)
      {
        using (var tbl = stbl.GetTable())
          kg = tbl.GetDatastore() as KnowledgeGraph;
        //TODO use KnowledgeGraph
      }
    }
  });
}