LINQ Range Variable Problem

Oct 5 2010 4:24 AM

Ran into this issue last night and just figured it out. I have this code for a demo:

using System;
using System.Data.Objects;
using System.Transactions;
using ExtractTransformLoad.Domain;
using Northwind.Entities;
//using System.Linq;

namespace ExtractTransformLoad
{
    public class SqlFreightByShipperRepository : IFreightByShipperRepository
    {
        public void DeleteAndInsert(DateTime runDate, FreightByShipper freightByShipper)
        {
            using (var context = new NorthwindEntities())
            using (var scope = new TransactionScope())
            {
                var summaryToDelete = (from freightSummary in context.FreightSummaries
                                       where
                                           freightSummary.RunDate == runDate &&
                                           freightSummary.ShipperName == freightByShipper.ShipperName

                                       select freightSummary);//.FirstOrDefault();
                context.DeleteObject(summaryToDelete);

                var newFreightSummary = new FreightSummary()
                                         {
                                             Freight = freightByShipper.Freight,
                                             RunDate = DateTime.Today,
                                             ShipperName = freightByShipper.ShipperName
                                         };
                context.FreightSummaries.AddObject(newFreightSummary);
                context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
                scope.Complete();
            }
        }
    }
}

Now, in Visual Studio, it looks like this:

Hovering over freightSummary in the above LINQ query would reveal just

(range variable) ? freightSummary

A bunch of searching later didn’t much help, although this thread did put me on the right track just a moment ago. The trick, it turns out, is that I didn’t have the System.Linq namespace included (you can see above I just re-commented it out). If you include System.Linq, everything works as expected. Final code here:

using System;
using System.Data.Objects;
using System.Transactions;
using ExtractTransformLoad.Domain;
using Northwind.Entities;
using System.Linq;

namespace ExtractTransformLoad
{
    public class SqlFreightByShipperRepository : IFreightByShipperRepository
    {
        public void DeleteAndInsert(DateTime runDate, FreightByShipper freightByShipper)
        {
            using (var context = new NorthwindEntities())
            using (var scope = new TransactionScope())
            {
                var summaryToDelete = (from freightSummary in context.FreightSummaries
                                       where
                                           freightSummary.RunDate == runDate &&
                                           freightSummary.ShipperName == freightByShipper.ShipperName

                                       select freightSummary).FirstOrDefault();
                context.DeleteObject(summaryToDelete);

                var newFreightSummary = new FreightSummary()
                                         {
                                             Freight = freightByShipper.Freight,
                                             RunDate = DateTime.Today,
                                             ShipperName = freightByShipper.ShipperName
                                         };
                context.FreightSummaries.AddObject(newFreightSummary);
                context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
                scope.Complete();
            }
        }
    }
}

I guess I’m spoiled by Resharper, which normally prompts me for any namespace it detects that I’m trying to use but haven’t yet included. It wasn’t until I added the .FirstOrDefault() that R# kicked in, and then for some reason it couldn’t automatically add the using statement for System.Linq, but once I did so by hand, the Range Variable problem disappeared.