Assuming that the element of the collection parameter are of type MyObjectClass:
List<MyObjectClass> SelectedItemsList{get;set;}
private void DataGridSelectionChanged(object selectedBackPlaneData)
{
SelectedItemsList= (selectedBackPlaneData as IList).Cast<MyObjectClass>().ToList();
}
will do the trick.
You could also use a generic:
private IList<t> ConvertListOfSelectedItem<t>(object param)
{
return (param as IList).Cast<t>().ToList();
}
In which case the code would be
IList<MyObjectClass> SelectedItemsList{get;set;}
private void DataGridSelectionChanged(object stuff)
{
SelectedItemsList= ConvertListOfSelectedItem<MyObjectClass>(stuff);
}