linq - C# Filter List to remove any double object -

have searched ant tested many examples in forum can't working method.

i using linq bulk insert list of entity classes (remotereadings).

due unique constraints need filter out items inserted.

uniqiuness composed of 2 columns meterid , datetime in remotereadings table.

// approx 5000 records (i need in batches of 2000 due  // constraint in l2s,but can after working) list<remotereading> lst = createlistfromcsv();   // option 1: // not work comparing memory list db list. need use contains() method. // trying accomplish infollowing examples.  list<remotereading> mylst = (from ri in db.remotereadings                                                                                    l in lst                              l.meterid = ri.meterid                              && l.date = r.date                             select ri).tolist(); ////  // option2: // list db in memory lst  list<remotereading> mylst = (from ri in db.remotereadings                                                                                                                 // in list comparing meaterid , datemeaured                             (from l in lst                             select  /// here ! ///                             select ri).tolist<remoteinterconnectorreading>();   // option3: // list lst not in database // bit confused here !   // tried remove list duplicates:  list<remotereading> result = list<remotereading>)mylst.except(lst).tolist<remotereading>();   // db.remotereading.insertallonsubmit(result); db.submitchanges(); 

any please?

due limitations in ef, can't join db query in-memory list. also, contains can used primitive list. need make efforts find duplicates on 2 columns.

var newitems = createlistfromcsv(); var meterids = newitems.select(n=> n.meterid).distinct().tolist(); var dates = newitems.select(n=> n.date).distinct().tolist();  var probablematches = (from ri in db.remotereadings                                                     (meterids.contains(ri.meterids)                       || dates.contains(ri.date)                       select new {ri.merterid, ri.date}).tolist();  var duplicates = (from existingri in probalematches                  join newri in newitems                  on new {existingri.meterid, existingri.date}                  equals {newri.meterid, newri.date}                  select newri).tolist();  var insertlist = newitems.except(duplicates).tolist();  db.remotereadings.insert(insertlist); // or whatever