Hello Jean-Pierre,

Thank you for the code-snippet you have provided.

The SelectedDataItems property of the XamDataGrid is of type - object array (object[]). A binding between this property and a collection will not result in a success.
I can suggest you create a property of type object[] as well inside the ViewModel class and bind to it.

XAML:

<igDP:XamDataGrid Name="XDT"
                    DataSource="{Binding Path=Items}"
                    SelectedDataItems="{Binding Path=MySelectedDataItems, Mode=TwoWay}"
                    SelectedDataItemsScope="RecordsOnly"/>

Code-behind:

public class ViewModel
{
    public object[] MySelectedDataItems { get; set; }
}

In order to bind a collection to the SelectedDataItems, the best approach would be to use a converter for the binding, which will allow us to transfer the items from the array to a newly created collection.

I have attached a sample application that demonstrates the initial approach from above.

If you have any questions, please let me know.