title: QueryableCollectionView with datagrid and dataform - selection changed issue
body: <p>I have an mvvm solution. In my <code>viewModel</code> I have an <code>QueryableCollectionView</code> of the class <code>BaseClass</code> objects and an standalone <code>BaseClass</code> element(let's call it seletedElem).</p>
  
  <p>The <code>BaseClass</code> have a private <code>QueryableCollection</code> of the <code>ChildClass</code> objects - <code>SCollection</code>, and a property that returns this collection. Both classes are implementing the following interfaces:  <code>INotifyPropertyChanged</code>, <code>IDataErrorInfo</code>, <code>IEditableObject</code>. In my view I have <code>raddatagrid</code> which <code>itemssource</code> is binded to the <code>ObservableCollection</code> of <code>BaseClass</code> objects from <code>viewModel</code> and selected item is binded to the standalone <code>BaseClass</code> object - <code>selectedElem</code>.</p>
  
  <p>The Dataform is binded to the currently selected grid item in this way :</p>
  
  <pre><code>ItemsSource="{Binding ElementName=xxx,Path=DataContext.seletedElem.SCollection}"
  </code></pre>
  
  <p>Then before the first DataGrid's selection changed event, or after the new item is inserted to the grid, when I press add button of the <code>raddataform</code> the current item of the <code>SCollection</code> is always an empty item of type <code>ChildClass</code>, but after the grid's selection changed event(when one of the existing items is selected) the current item of the <code>SCollection</code> is always null and I'm unable to edit it's properties.</p>
  
  <p>The <code>dataGrid</code> and <code>dataform</code> are Telerik components. </p>
  
  <p>Is there anyway to fix this behavior?</p>