Linq to SQL OrderBy issue

Question

I know this question has been asked many times and I know that the Distinct call destroys the previous order so I must use the OrderBy afterwards, but in this case I must be doing something else wrong.

int[] resources = (from a in context.Beamline_Requests
                   join b in context.Technique_Requests on a.Technique_Request_ID equals b.ID
                   where b.Beamtime_Request_ID == id
                   select a.Beamline_ID).Distinct().OrderBy(a => a.ID).ToArray();

I receive the:

Cannot convert lambda expression to type 'System.Linq.Expressions.LambdaExpression' because it is not a delegate type

error message on the OrderBy. It also says:

'int' does not contain a definition for 'ID' and no extension method 'ID' accepting a first argument of type 'int' could be found (are you missing a using directive or an assembly reference?)

So apparently the 'a' is no longer part of the context.

I have done similar things successfully but in those cases I am projecting the Linq into a ViewModel so in this case it must have something to do with attempting to just make it an array.

Answer 1

You are only selecting field Beamline_ID and later you are trying to OrderBy ID, Your intermediate result from select doesn't have field ID it is just a projection of int numbers. As @GrantWinney suggested you can do OrderBy(a=> a) like:

int[] resources = (from a in context.Beamline_Requests
                   join b in context.Technique_Requests on a.Technique_Request_ID equals b.ID
                   where b.Beamtime_Request_ID == id
                   select a.Beamline_ID).Distinct().OrderBy(a => a).ToArray();

For the comment:

My issue though is that I actually do need to order by the ID, not the Beamline_ID even though I only need the Beamline_ID in the array.

int[] resources = (from a in context.Beamline_Requests
                   join b in context.Technique_Requests on a.Technique_Request_ID equals b.ID
                   where b.Beamtime_Request_ID == id
                   select new 
                   { 
                       Beamline_ID = a.Beamline_ID,
                       ID = b.ID
                   })
                   .OrderBy(a => a.ID)
                   .Select(r=> r.Beamline_ID)
                   .Distinct()
                   .ToArray();

Or in a simpler version you can achieve:

int[] resources = (from a in context.Beamline_Requests
                   join b in context.Technique_Requests on a.Technique_Request_ID equals b.ID
                   where b.Beamtime_Request_ID == id
                   orderby b.ID
                   select a.Beamline_ID)
                   .Distinct()
                   .ToArray();