public sealed class ProjectWindowSelectedItemsChangedEvent : ArcGIS.Core.Events.CompositePresentationEvent<ProjectWindowSelectedItemsChangedEventArgs> 

{
  // subscribe to event
  ProjectWindowSelectedItemsChangedEvent.Subscribe(args =>
  {
    if (args.IProjectWindow.SelectionCount > 0)
    {
      // get the first selected item
      var selectedItem = args.IProjectWindow.SelectedItems.First();

      // Note: Needs QueuedTask to run
      // datasetType
      var dataType = ItemFactory.Instance.GetDatasetType(selectedItem);
      // get the dataset Definition
      if (ItemFactory.Instance.CanGetDefinition(selectedItem))
      {
        using var def = ItemFactory.Instance.GetDefinition(selectedItem);
        if (def is FeatureClassDefinition fcDef)
        {
          var oidField = fcDef.GetObjectIDField();
          var shapeField = fcDef.GetShapeField();
          var shapeType = fcDef.GetShapeType();
        }
        else if (def is ArcGIS.Core.Data.Parcels.ParcelFabricDefinition pfDef)
        {
          string ver = pfDef.GetSchemaVersion();
          bool enabled = pfDef.GetTopologyEnabled();
        }
      }
      // get the dataset
      if (ItemFactory.Instance.CanGetDataset(selectedItem))
      {
        using var ds = ItemFactory.Instance.GetDataset(selectedItem);
        if (ds is FeatureDataset fds)
        {
          // open featureclasses within the feature dataset
          // var fcPoint = fds.OpenDataset<FeatureClass>("Point");
          // var fcPolyline = fds.OpenDataset<FeatureClass>("Polyline");
        }
        else if (ds is FeatureClass fc)
        {
          var name = fc.GetName() + "_copy";
          // create
          var featureLayerParams = new FeatureLayerCreationParams(fc)
          {
            Name = name,
            MapMemberIndex = 0
          };
          LayerFactory.Instance.CreateLayer<FeatureLayer>(featureLayerParams, MapView.Active.Map);
        }
        else if (ds is Table table)
        {
          var name = table.GetName() + "_copy";
          var tableParams = new StandaloneTableCreationParams(table)
          {
            Name = name
          };
          // create
          StandaloneTableFactory.Instance.CreateStandaloneTable(tableParams, MapView.Active.Map);
        }
      }
    }
  });
}