public ReadOnlyObservableCollection<Element> GetSelectedElements()

//on the QueuedTask  
var elementsToRemove = layout.GetSelectedElements();
layout.DeleteElements(elementsToRemove);

//on the QueuedTask
var elemsToGroup = layout.GetSelectedElements();
//Note: run within the QueuedTask
//group  elements
var groupElement = layout.GroupElements(elemsToGroup);

//On the QueuedTask
//get the current selection set
var sel_elems = layout.GetSelectedElements();
//can they be brought forward? This will also check that all elements have the same parent
if (layout.CanBringForward(sel_elems))
{
  //bring forward
  layout.BringForward(sel_elems);
  //bring to front (of parent)
  //graphicsLayer.BringToFront(sel_elems);
}
else if (layout.CanSendBackward(sel_elems))
{
  //send back
  layout.SendBackward(sel_elems);
  //send to the back (of parent)
  //graphicsLayer.SendToBack(sel_elems);
}

var selElementsZOrder = layout.GetSelectedElements();
//list out the z order
foreach (var elem in selElementsZOrder)
  //At 2.x - System.Diagnostics.Debug.WriteLine($"{elem.Name}: z-order {elem.GetZOrder()}");
  System.Diagnostics.Debug.WriteLine($"{elem.Name}: z-order {elem.ZOrder}");