title: ViewModel to ViewModel Communication
body: <p>Given the following scenario:</p>
  
  <ol>
  <li>ViewModelA launches ViewModelB (via a common Controller, of course, that uses Ioc and DI to resolve the types needed).</li>
  <li>ViewModelB needs to set a property value in ViewModelA.</li>
  </ol>
  
  <p>Is it bad to simply inject ViewModelA into ViewModelB via constructor injection and just set the property directly?</p>
  
  <p>Or…</p>
  
  <p>Should a messaging system like the EventAggregator from Prism be used to handle all communication between ViewModels?</p>
  
  <p>I like the injection approach because it’s easy, but my instincts are telling me I’m missing something.  I call on your collective wisdom to help fill in my blind spot.</p>