CODEWITHSUNDEEP
linqlinq-to-sql
Glinkot
Glinkot

Reputation: 2964

LINQ FirstOrDefault problem

I am stuck on a LINQ query. Basically I have two tables linked by association on a uniqueID key. One table contains things that look duplicated (tblDupes), another is the fact table (tblVouchers). In the below query my 'sum' is working, but the FirstorDefault does not. It returns an error 'cannot implicitly convert type 'string' to 'bool'.

var dupeGroups = from d in db.tblDupes
                           group d by d.dupeGroup into g
                           select new 
                           { 
                               Group = g.Key, 
                               TotalVal = g.Sum(v => v.tblVoucher.TransactionAmtDecimal),
                               Vendor = g.FirstOrDefault(x => x.tblVoucher.vendorName)
                            };

Any ideas? I've tried many different permutations of FirstOrDefault, putting it at the end, etc etc. I've also tried First().

Thanks!

Upvotes: 3

Views: 4318

Answers (2)

Mark Carpenter
Mark Carpenter

Reputation: 17775

I think that the parameter to FirstOrDefault is a predicate used for filtering. You want to select the field you want to retrieve first, and then grab the first result (methinks) like this:

var dupeGroups = from d in db.tblDupes
                 group d by d.dupeGroup into g
                 select new { 
                     Group = g.Key, 
                     TotalVal = g.Sum(v => v.tblVoucher.TransactionAmtDecimal),
                     Vendor = g.Select(x => x.tblVoucher.vendorName).FirstOrDefault()
                 };

Hope this helps!

Upvotes: 3

Kirk Woll
Kirk Woll

Reputation: 77546

FirstOrDefault takes a predicate, meaning a Func<T, bool>. However, you are passing, x => x.tblVoucher.vendorName, a Func<T, string>, since vendorName is a string. The bool result is to indicate the first row that matches. For example, to find the first row with a vendorName equal to "foo", you would pass in x => x.tblVoucher.vendorName == "foo".

Upvotes: 4

Related Questions