title: Displaying progress of processing collection
body: <p>I'm wondering what is a best practice to handle processing a collection of items and display the progress back to the UI.</p>
  
  <p>The following code is roughly what I wrote to handle it, but it seems quite dirty:</p>
  
  <pre><code>Command = ReactiveCommand.CreateAsyncTask(_ =&gt; {
     return Task.Run(() =&gt; 
     {
         Parallel.ForEach(items, item =&gt;
         {
             RunSlowProcess(item);
  
             Application.Current.Dispatcher.BeginInvoke(x =&gt;
             {
                 Progress += 1;
             }
         });
     }
  }
  </code></pre>
  
  <p>Is there some major concept of ReactiveUI that I'm missing?</p>