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

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

    await QueuedTask.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 ArcGIS.Core.Data.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();
          }

          // etc
        }
      }

      // get the dataset
      if (ItemFactory.Instance.CanGetDataset(selectedItem))
      {
        using (var ds = ItemFactory.Instance.GetDataset(selectedItem))
        {
          if (ds is ArcGIS.Core.Data.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);
          }
        }
      }
    });
  }
});