linq->SQL orderby descending not working

问题

var Customer = (from c in DNAContextSQL.Customers
                                where c.LastName != ""
                                orderby c.PKID_Customer descending
                                select new
                                {
                                    c.PKID_Customer,
                                    c.OrganizationName,
                                    c.FirstName,
                                    c.LastName,
                                    c.Phone,
                                    c.Extension
                                }).Distinct().ToList();

I know this is basic. I can't find any good reason why it's not working though. The queries sent to SQL Profiler don't seem to have an order by clause in them.

Any ideas?

I can get it to work with .OrderByDescending(...) but would like to know the reason behind this madness.

回答1:

The distinct is probably messing up the order by try calling the orderBy after the distinct()

var Customer = (from c in DNAContextSQL.Customers
                where c.LastName != ""
                select new
                   {
                      c.PKID_Customer,
                      c.OrganizationName,
                      c.FirstName,
                      c.LastName,
                      c.Phone,
                      c.Extension
                    }
                ).Distinct().OrderByDescending(c=>c.PKID_Customer).ToList();

This is happening because you first select a set of rows that are ordered by the PKID_Customer (and they are ordered until you call the distinct() method), and after that the Distinct() method rearranges them into a new distinct unordered set of records.

来源：https://stackoverflow.com/questions/6431319/linq-sql-orderby-descending-not-working