GridView and collection reorder, SelectedItem becomes null

[Chris]

I am using MVVM pattern.  I have a RadGridView and have bound the ItemsSource to a collection and SelectedItem to an individual item in the VM.    This works, and I have some buttons to reorder the collection.  They call a command on the VM that moves the SelectedItem up or down in the collection.  This works fine but it appears that after the item gets moved, the SelectedItem becomes null.  My goal is to be able to select an item in the RadGridView and then click the "Move Up" button several times to move the item up in the collection.  Currently the experienced behavior is that I click the item and get one Move Up(or Down) before the SelectedItem becomes null and I am required to select an item to continue moving items.  I have put debug statements in both the SelectionChanged and SelectionChanging events on the RadGridView. 

Upon running my app, here is the order I see:

Event	SelectedItem
SelectionChanging	null
SelectionChanged	CorrectItem
Move method	CorrectItem
SelectionChanging	CorrectItem
SelectionChanged	null

I even tried manually setting the SelectedItem in the VM after reordering it, but the reset to null appears to happen sometime after this. 
I have the latest version (2013.1.220.45)  installed and referenced in my project.
   Please let me know if something is unclear.

Thanks,
Chris

[Dimitrina]

Hi Chris,

May I ask you to share the code implementation for the "Move Up" button click (how do you move the item)?
  

Regards,
Didie
the Telerik team

[Chris]

Didie,

I created a sample application to demonstrate the behavior.  Then when I tested it, the up and down movement of items within the collection was working as expected.  I then added in the XAML properties I had applied to my RadGridView in my original project.  The problem resurfaced.  I narrowed it down to the IsFilteringAllowed="False" property.  Once I set this, the SelectedItem become null after the operation is performed.  I can submit the demo application if you would like.

Thanks,
Chris

[Dimitrina]

Hello Chris,

Yes, please. You can open a support ticket and send us the demo project. 

All the best,
Didie
the Telerik team

[Andie]

When you RaisePropertyChange on the ItemsSource it will always reset your SelectedValue. The way I get around this is by putting a flag in my setter for the SelectedValue in the ViewModel to not allow PropertyChange

_allowSelectedItemsPropertyChange = false;
RaisePropertyChagne(()=>  ItemSourceInViewModel )

_allowSelectedItemsPropertyChange = true;

   public object SelecedValueInViewModel
        {
            get
            {
                return _selectedValue
            }
            set
            {
                if (_allowSelectedItemsPropertyChange)
                {

                        selectedValue= value
                   }
                RaisePropertyChanged(() => SelecedValueInViewModel);

            }
        }