private static Func <DependencyObject, bool> GetTemplatedChildExpandPredicate(IDataGridItemContainer source)
{
var fe = source as FrameworkElement;
if (fe == null)
{
throw new ArgumentException("The source object must be a FrameworkElement.", "source");
}
return(( DependencyObject item ) => IDataGridItemContainerExtensions.ExpandChild(item) &&
IDataGridItemContainerExtensions.IsPartOfTargetTemplate(item, fe));
}