How to group then select items into a new class in LINQ (C # preferred)

Hi I'm trying to figure out the grouping and then create my own class as a result. I know that the result of the group is an IGrouping collection, but can I access the rows as they are instantiated to add a couple of flags with a custom class to them?

I have a FlightTimes class with some data, but I would like to add some data to the rows, like FlagRedEye. So I created a FlightTimeResult class with the original FlightTime class data plus a flag.

Can I do it? I can't figure out how to get it to work. I like to use strong types until I understand what's going on. I had to change a few things to protect my client, so I apologize for any syntax errors.

IGrouping<string, FlightTimeResult> FlightTimes =
               ( from flighttimes in schedules.FlightTimes
                 group flighttimes by flighttimes.FlightType.ToString()
                     into groupedFlights
                 select new FlightTimeResult( )
                     FlightTimeData = FlightTime,   // Original class data
                     FlagRedEye = (FlightTime.departureTime.Hour >= 0 &&
                                  FlightTime.departureTime.Hour < 6) // Extra flag
                 } )


The goal is to have a FlightTimesResult set (optional FlightTime + flag) grouped by FlightType. Not sure how to access individual FlightTime lines in the "select new FlightTimeResult ()" query

Do I need to use subquery in groupedFlights?

Many thanks.


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2 answers

This is most easily obtained by explicitly calling the Linq functions like this:

IQueryable<IGrouping<string, FlightTimeResult>> query 
         = schedules.FlightTimes.GroupBy(
               ft => ft.FlightType.ToString(), // key 
               ft => new FlightTimeResult() { // your constructed objects for key
                    FlightTimeData = ft,
                    FlagRedEye = (ft.departureTime.Hour >= 0 && ft.departureTime.Hour < 6)


The two argument operation takes two lambda arguments as arguments - one to retrieve the keys, and one to retrieve the values ​​for it.GroupBy

Also keep in mind that a group by operation (whether building group itm by key

or calling GroupBy

) returns a collection IGrouping<,>

- none.

So it will be IEnumerable<IGrouping<,>>

or IQueryable<IGrouping<,>>




I think you are on the right track. Instead of grouping FlightTimes by FlightType, try creating FlightTimeResults and grouping them using FlightType:

var results = 
    from ft in schedules.FlightTimes
    group new FlightTimeResult
            FlightTimeData = ft,
            FlagRedeye = ft.DepartureTime.Hour >= 0 && ft.DepartureTime.Hour < 6
    by ft.FlightType.ToString()
    into groupedFlights
    select groupedFlights;




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