title: ListView CollectionView sort lowest level
body: <p>I've a question about how to sort items in a ListView, I thought this would be really easy, but I can't seem to work it out.</p>
  <p>The ListView is bound to an observable collection view model... the items in the list view are grouped based on certain properties by setting up a CollectionViewSource and setting up GroupDescriptions:</p>
  <pre><code>            BrowserItemCollectionView = CollectionViewSource.GetDefaultView(_browser);
  
          //Set up filter
          BrowserItemCollectionView.Filter = FilterBrowserItems;
  
          //Set up grouping
          PropertyGroupDescription L1PGD = new PropertyGroupDescription(nameof(BrowserItem.L1group));
          PropertyGroupDescription L2PGD = new PropertyGroupDescription(nameof(BrowserItem.L2group));
          PropertyGroupDescription L3PGD = new PropertyGroupDescription(nameof(BrowserItem.L3group));
          BrowserItemCollectionView.GroupDescriptions.Add(L1PGD);
          BrowserItemCollectionView.GroupDescriptions.Add(L2PGD);
          BrowserItemCollectionView.GroupDescriptions.Add(L3PGD);
  </code></pre>
  <p>I then sort the groups with:</p>
  <pre><code>        //Setup Sorting
          BrowserItemCollectionView.SortDescriptions.Add(new SortDescription(nameof(BrowserItem.L1group), ListSortDirection.Descending));
          BrowserItemCollectionView.SortDescriptions.Add(new SortDescription(nameof(BrowserItem.L2group), ListSortDirection.Descending));
          BrowserItemCollectionView.SortDescriptions.Add(new SortDescription(nameof(BrowserItem.L3group), ListSortDirection.Descending));
  </code></pre>
  <p>This works well and sorts the groupings in Descending order.</p>
  <p>What I now what to do is sort the actual items - the objects that are the lowest levels of the tree views.</p>
  <p>What method do I use to sort the actual list view items?</p>
  <p>Thanks.</p>