Using max() function with entity framework throws an exception

Question

Using max() function with entity framework throws an exception

entity-framework max

Question

So I need to get the max value of a column (or the last one) using entity framework and both of these queries throw exceptions:

(The ID I'm trying to retrieve is of type varchar, but it works in raw sql, I think it should work here too)

This one:

string maxCurrentID = db.reservations.Max().ReservationID;

Throws this:

The specified method 'EntityClub_.reservacion Maxreservacion' on the type 'System.Linq.Queryable' cannot be translated into a LINQ to Entities store expression because no overload matches the passed arguments.

and this one:

 string maxCurrentID = db.reservations.LastOrDefault().ReservationID;

LINQ to Entities does not recognize the method 'EntityClub_.reservacion LastOrDefaultreservacion' method, and this method cannot be translated into a store expression.

How can I obtain the expected values?

Alex Terreaux

Popular Answer

var maxReservationId=db.reservations.Max(u =>(int?)u.ReservationID) ?? 0;

if there is no data in table it replaces null with 0

sanjeet

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user743382 · Accepted Answer · 1/13/2013 8:18:19 AM

You aren't asking for the highest ReservationID, you're trying to get the highest Reservation, and getting its ReservationID. EF does not understand what "the highest Reservation" means.

var maxReservationID = db.reservations.Max(r => r.ReservationID);

or

var maxReservationID = db.reservations.Select(r => r.ReservationID).Max();

should work.

Using max() function with entity framework throws an exception

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