LINQ method to compare 2 lists

Question

There's just GOT TO BE a better way to do this. I am looking at 2000 lines of code that is creating a huge problem with performance and, of course, the "script isn't responding" message.

It's using linq to sql, linq to entities and a little of everything else.

The biggest problem by far I see is that there are dozens and dozens of foreach statements. Each of these looping through (sometimes more than once) a set of objects.

I'm not the best at linq entities methods but I know I've seen examples of .Contains and .Select where I think this would be a good alternative.

I know there has to be a LINQ Method that will do this more efficiently.

Here is a sample of what is happening:

  //RETURNS LIST<LandingPageVendorEvaluation>
  var evaluatedVendors = contactRecords.Where(x => x.VendorId > 0)
   .Select(x => new LandingPageVendorEvaluation()
            {
                ClientVendorId = x.ClientVendorId,
                VendorId = x.VendorId,
                VendorName = x.VendorName,
                Outcome =
                    selectedCount > 0
                        ? (x.VendorIsSelected ? OpportunityOutcomes.Win :
                     OpportunityOutcomes.Loss): OpportunityOutcomes.NoDecision,
                Selected = x.VendorIsSelected,
                IsClient = x.VendorIsClient,
                IsOther = x.VendorIsOther
            }).OrderBy(x => x.VendorName).Distinct().ToList();


           //  NOW a foreach to see if this list of 
           //  LandingPageVendorEvaluation objects is in another
           //  List<LandingPageVendorEvaluation >.  If it isn't there, 
           //  it's added

            foreach (var ev in evaluatedVendors)
            {
                if (profile.EvaluatedVendors.Where(v => v.VendorId == 
                  ev.VendorId).Count() == 0)
                {
                    profile.EvaluatedVendors.Add(ev);
                }
            }

Like I said, this is just an example. Some of these lists contain hundreds of entries.

Any suggestions?

Answer 1

You didn't say what contactRecords and profile exactly is, so it's hard to make sure how to solve the problem in best possible way, but following should do the trick:

var evaluatedVendors = contactRecords.Where(x => x.VendorId > 0)
   .Select(x => new LandingPageVendorEvaluation()
            {
                ClientVendorId = x.ClientVendorId,
                VendorId = x.VendorId,
                VendorName = x.VendorName,
                Outcome =
                    selectedCount > 0
                        ? (x.VendorIsSelected ? OpportunityOutcomes.Win :
                     OpportunityOutcomes.Loss): OpportunityOutcomes.NoDecision,
                Selected = x.VendorIsSelected,
                IsClient = x.VendorIsClient,
                IsOther = x.VendorIsOther
            }).OrderBy(x => x.VendorName).Distinct();

var vendorIds = profile.EvaluatedVendors.Select(v => v.VendorId);

var itemsToAdd = evaluatedVendors.Where(v => !vendorIds.Contains(v.VendorId)).ToList();

profile.EvaluatedVendors.AddRange(itemsToAdd);

However, because you didn't specify what profile is, it may not have AddRange method. If that's the case you can iterate over itemsToAdd instead and call Add instead.