Select distinct list from nested collections on multiple fields

Question

I am trying to get distinct list of nested object from collection using LINQ.

Please check the below scenario

I have list of ClientAccounts,in every client account there is list of Holdings and in each holding has Instrument Type. I am trying to get unique instrument list from list of client accounts.

So far I have tried with below query, but it returns all the instruments. clientAcccounts is list of Client Account.

List<Instrument> lstclientInstrument = clientAcccounts
                                          .SelectMany(x => x.Holdings)
                                          .Select(s => new Instrument { 
                                                          InstrumentID = s.Instrument.InstrumentID, 
                                                          AssetTypeID = s.Instrument.AssetTypeID 
                                                       })
                                          .Distinct()
                                          .ToList();

Any suggestion to get distinct list.

Instead of using Distinct use .GroupBy(x => x.InstrumentID).Select(x => x.FirstOrDefault()).ToList(); — jdweng, May 05 '18 at 11:52
Possible duplicate: https://stackoverflow.com/questions/8560884/how-to-implement-iequalitycomparer-to-return-distinct-values — mshwf, May 05 '18 at 12:10

score 4 · Accepted Answer · answered May 05 '18 at 12:02

4

Try This Group by with multiple Keys.

List<Instrument> ins = clientAcccounts.SelectMany(x => x.Holdings.Select(s => s.Instrument)).ToList().GroupBy(p=> new {p.InstrumentID,p.AssetTypeID},(key,group)=>group.First()).ToList<Instrument>();

answered May 05 '18 at 12:02

vinit jain

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Select distinct list from nested collections on multiple fields

1 Answers1