title: WPF MVVM service layer
body: <p>I plan on writing a WPF app following the MVVM pattern for the first time but something is not quite clear to me.  Let's say that the view has a "Save" button and when that is hit I need to save the current state of my data (the model).  This will be done by sending a SOAP message to a SOAP service.</p>
  
  <p>Where in my MVVM setup do these SOAP request/response handlers live?  Does the view model make the SOAP call itself whenever the save button is hit? Should the view model notify the model to save itself instead?  Maybe it's some other way, completely separate from the MVVM?  </p>
  
  <p>My thinking was that (at least in this specific case) the view model would handle it since it needs to disable the save button in the view until the current save request has completed.</p>