Linq join iquery, how to use defaultifempty

Question

I have written a linq join query and I would like to take the values, if one of them are empty...

Code:

var Details =   UnitOfWork.FlightDetails           .Query()           .Join           (               PassengersDetails,               x => x.Flightno,               y => y.FlightNo,               (x, y) => new               {                   y.PassengerId,                   y.classType,                   x.Flightno,                   x.FlightName,               }           ); 

I would like to use something like..

"Above query".DefaultIfEmpty (     new      {         y.PassengerId,         y.classType,         string.Empty,         string.Empty     } ); 

FlightDetails is Idatarepository type on a class and PassengerDetails is IQueryable local variable result. How can I get result with PassengerId and Classtype without flightno and flightname included in the overall results?

Answer 1

You basically want to do a left outer join. The way you currently are using the DefaultIfEmpty method is that if the entire list is empty you provide a single default entry.

You should join with PassengerDetails and for each passenger details list call the default if empty. This is the equivalent of a left outer join and it goes a little something like this:

var data = from fd in FlightDetails            join pd in PassengersDetails on fd.Flightno equals pd.FlightNo into joinedT            from pd in joinedT.DefaultIfEmpty()            select new {                          nr = fd.Flightno,                          name = fd.FlightName,                          passengerId = pd == null ? String.Empty : pd.PassengerId,                          passengerType = pd == null ? String.Empty : pd.PassengerType                        }