LINQ: dot notation equivalent for JOIN

问题

Consider this LINQ expression written using query notation:

 List<Person> pr = (from p in db.Persons
                     join e in db.PersonExceptions
                     on p.ID equals e.PersonID
                     where e.CreatedOn >= fromDate
                     orderby e.CreatedOn descending
                     select p)
                   .ToList();

Question: how would you write this LINQ expression using dot notation?

回答1:

Like this:

List<Person> pr = db.Persons
                    .Join(db.PersonExceptions,
                          p => p.ID,
                          e => e.PersonID,
                          (p, e) => new { p, e })
                    .Where(z => z.e.CreatedOn >= fromDate)
                    .OrderByDescending(z => z.e.CreatedOn)
                    .Select(z => z.p)
                    .ToList();

Note how a new anonymous type is introduced to carry both the p and e bits forward. In the specification, query operators which do this use transparent identifiers to indicate the behaviour.

来源：https://stackoverflow.com/questions/1511833/linq-dot-notation-equivalent-for-join