Question

I am trying to convert this T-SQL to a Linq To SQL but can’t work out the group by aggregate functions. Any help welcome.

select c.ClientID, GivenName, Surname, max(a.Address), max(t.Value)
from Client c
left join ClientAddress a on c.ClientID = a.ClientID
left join ClientContact t on c.ClientID = t.ClientID
group by c.ClientID, GivenName, Surname

Answer 1

To group by a composite key, you typically use an anonymous type:

    var qry = from x in someSource
              group x by new { x.ClientID, x.GivenName, x.Surname } into grp
              select new { grp.Key, Address = grp.Max(x => x.Address),
                  Value = grp.Max(x => x.Value) };