double GetRotation()

//Modify and element's rotation value.

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  double elmRot = element.GetRotation();
  elmRot = 22.5;

  element.SetRotation(elmRot); //You don't have to get to set; a shortcut would be: element.SetRotation(22.5);
});