title: How to replace Spinner with UIProgress view?
body: <p>I am relatively new to iOS Xamarin c# development.</p>
  
  <p>I created an app for an iPad which on demand(button DownloadDocuments) downloads documents for offline use.
  While download is in progress the "Loading overlay" is shown with the "spinner". The app is in use and everything works great...but.
  Now the client wants to see a Progress bar instead of a spinner. 
  The design is: Master-Detail controller, button is in master, downloading is performed by a procedure in "Utilities" class.</p>
  
  <p>I've read so many posts in all kins of forums, but this Threading matter is still very much "terra Nova" to me.</p>
  
  <p>I coded the UIProgressView into Loading overlay and I can see it, if I assign some 0.5f value to the Progress property. 
  How do IO make the progress move?</p>
  
  <p>Where(if I have to) do I invoke the new thread and progress value assignment:
  - in Utilities.DounloadDocuments? 
  - In the cycle of downloading files(I'm using WebClient)?
  - In the button handler?</p>
  
  <p>Could somebody help me, please.</p>