title: Is it possible for some messagebus subscriblers to handle message in UI thread, some others in background thread?
body: <p>I'm using ReactiveUI's <code>RegisterScheduler</code> like this:</p>
  
  <p><code>MessageBus.Current.RegisterScheduler&lt;string&gt;(RxApp.MainThreadScheduler, someContract);
  </code></p>
  
  <p>I want some of the message subscribers (who register this message) handle it in UI thread, but at the same time, some other subscribers handle it in backgroud thread.</p>
  
  <p>Here is the use case: Some of the message's subscribers will handle UI related data which must happen in UI thread. But I want to reduce the UI thread usage as minimum as possible, so I would like to have other operations (not related to UI) happen in background thread. Is it possible for ReactiveUI?</p>
  
  <p>My current solution is to use 2 different contract string, which in fact can be considered 2 different messages. It works, but both messages should be send out together, which makes me feel reduntent.</p>
  
  <p>Any ideas?</p>
  
  <p>Fei</p>