LINQ - Different syntax style, different result?

Question

Can someone tell me the difference the following two LINQ statements please?

var ChkUnique = DB.BusinessFile.FirstOrDefault(c => c.ROCNo == txtBoxID.Text);

and

var ChkUnique = from c in DB.BusinessFile 
                where c.ROCNo == (string)txtBoxID.Text 
                select c;

ChkUnique != null returns false for the top one when a match cannot be found and true for the latter and I can't figure out why this is happening.

I'm new to LINQ so I could have missed something really basic but its driving me nuts at the moment.

Answer 1

The second code is returning an object that represents the query you are calling; it will never be null. Though once enumerated, it could be an empty collection. (still not null, though)

Your first is calling FirstOrDefault, which is forcing a single result into a single variable, returning null if there are no results. If you did Where instead of FirstOrDefault, you would have the same result both times.