LINQ to Entities GroupBy之后不能用Distinct？

[ylynet]

  var result = q.GroupBy(g => g.CREATE_USER).Select(s => new
            {
                userName = s.Key,
                count =s.Select(se=>se.PURCHASE_ITEM.PRODUCT_ID).Distinct().Count(),
                quantity = s.Sum(ss => ss.TRANSFER_QUANTITY)
            });

去掉 Distinct就没问题

[q107770540]

1. what is the error message? 2. are you sure se.PURCHASE_ITEM is not null ?