Question

Ive been struggling to find an answer to this task problem I am solving, despite spending the morning no here searching.
I have looked into the MIN/MAX clauses but cannot seem to fit it in my scenario properly.

I am performing this simple LINQ query where i search all rows where the column matches

using (DataClasses2DataContext db = new DataClasses2DataContext())
        {
            var routes = (

                          from txcalllines in db.TxcAllLines
                          where
                              txcalllines.LineName == searchString
                          select txcalllines);

            return routes.ToList();
        }

And this returns these results:

FILE                           LINE   START               FINISH
output_txc_45486m.xml           486   North Station       Friswell Place
SVRAYAO486-20121008-22264.xml   486   Dunoon              Inveraray
SVRAYAO486-20121008-22265.xml   486   Dunoon              Inveraray
SVRAYAO486-20121008-22266.xml   486   Dunoon              Inveraray
SVRGMB04860-20120103-5774.xml   486   BURY                RADCLIFFE
SVRGMB04860-20120103-5775.xml   486   BURY                RADCLIFFE
SVRYNAO486-20120217-44588.xml   486   Selby Bus Stn       Pollington Circular

The problem is, running this query returns several rows of the same route (you can see LINE, START, and FINISH are the same), where I only want to return the first matching row of each route.

So the desired result would be:

FILE                           LINE   START               FINISH
output_txc_45486m.xml           486   North Station       Friswell Place
SVRAYAO486-20121008-22264.xml   486   Dunoon              Inveraray
SVRGMB04860-20120103-5774.xml   486   BURY                RADCLIFFE
SVRYNAO486-20120217-44588.xml   486   Selby Bus Stn       Pollington Circular

Answer 1

You can use GroupBy then get the first element of each group.

var routes = (from txcalllines in db.TxcAllLines
              where txcalllines.LineName == searchString
              group txcalllines by new { txcalllines.Start, txcalllines.Finish } into g  // Groups the txcalllines by the pair (Start, Finish)
              select g.First());  // Gets the first intem of the group