title: DeferRefresh' is not allowed during an AddNew or EditItem transaction
body: <p>I am doing sorting in WPF on button click and use drag and drop technique
  when I drag a <code>dll</code> file in WPF and then click again on button for sorting.</p>
  
  <p>It gives an error of <code>DeferRefresh</code> is not allowed during an <code>AddNew</code> or EditItem transaction.</p>
  
  <p>//My sorting code </p>
  
  <pre><code>if (_sortColumn == column)
          {
  
              _sortColumn = column;
  
              downImage = @"..\Images\icon-arrow-up-b-128.png";
  
              NotifyOfPropertyChange(() =&gt; FilesView);
  
                  _filesCollectionViewSource.SortDescriptions.Add(new SortDescription(_sortColumn, System.ComponentModel.ListSortDirection.Ascending));
                  NotifyOfPropertyChange(() =&gt; DisplayedImageDown);
                  _filesCollectionViewSource.SortDescriptions.Clear();
                  _sortColumn = "";
      }
  }
  </code></pre>
  
  <p>//My Drag code</p>
  
  <pre><code>        string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
          List&lt;string&gt; fileList = new List&lt;string&gt;(files);
          List&lt;string&gt; filepaths = new List&lt;string&gt;();
          foreach (var file in (string[])e.Data.GetData(DataFormats.FileDrop, false))
          {
              FileInfo fi = new FileInfo(file);
              Console.WriteLine(fi.Name);
              long byteSize = fi.Length;
              //string stringSize = BytesToString(byteSize);
              string name = fi.Name;
  
              ListView listView = sender as ListView;
  
             ((ListCollectionView)FilesView.ItemsSource).AddNewItem((new FileViewModel(@"" + fi.DirectoryName + "/" + name)));//, itemSize = stringSize
  
  
  }
  </code></pre>
  
  <p>Can anyone help me?</p>