public Dictionary<T,List<long>> ToDictionary<T>()
where T: MapMember

{
  // Loads the selected features into an Inspector instance.
  // get the first layer and its corresponding selected feature OIDs
  var firstSelectionSet = selectedFeatures.ToDictionary().First();
  // create an instance of the inspector class
  var inspector = new Inspector();
  // load the selected features into the inspector using a list of object IDs
  await inspector.LoadAsync(firstSelectionSet.Key, firstSelectionSet.Value);
}

// Retrieves the value of a specific attribute and the geometry of the first selected feature from the provided selection set.
await QueuedTask.Run(() =>
{
  // get the first layer and its corresponding selected feature OIDs
  var firstSelectionSet = selectedFeatures.ToDictionary().First();

  // create an instance of the inspector class
  var inspector = new Inspector();

  // load the selected features into the inspector using a list of object IDs
  inspector.Load(firstSelectionSet.Key, firstSelectionSet.Value);

  //get the value of
  var pscode = inspector["STATE_NAME"];
  var myGeometry = inspector.Shape;
});

{
    MapMember us_zips_layer = map.GetLayersAsFlattenedList().OfType<FeatureLayer>().First(s => s.Name == "USA zips layer");

    var addToSelection = new Dictionary<MapMember, List<long>>();
    addToSelection.Add(us_zips_layer, new List<long> { 1506, 2696, 2246, 1647, 948 });
    //Create a SelectionSet object
    var selSet = ArcGIS.Desktop.Mapping.SelectionSet.FromDictionary(addToSelection);
    var selSetDict = selSet.ToDictionary();

    // convert to the dictionary and only include those that are of type FeatureLayer
    var selSetDictFeatureLayer = selSet.ToDictionary<FeatureLayer>();
}

{
    MapMember us_zips_layer = map.GetLayersAsFlattenedList().OfType<FeatureLayer>().First(s => s.Name == "USA zips layer");

    var addToSelection = new Dictionary<MapMember, List<long>>();
    addToSelection.Add(us_zips_layer, new List<long> { 1506, 2696, 2246, 1647, 948 });
    //Create a SelectionSet object
    var selSet = ArcGIS.Desktop.Mapping.SelectionSet.FromDictionary(addToSelection);

    var kvp = selSet.ToDictionary().Where(kvp => kvp.Key.Name == "LayerName").FirstOrDefault();
    var oidList = kvp.Value;
}