Hi Frans

If I run this query:

var query = from c in meta.Customer
        where c.CustomerId == "CustomerThatDoesNotExist"
        select c;

Console.WriteLine(query.FirstOrDefault() == null);

Then an "ArgumentOutOfRange" exception is thrown because the query returns no results (which is the same behaviour as calling First()).

With Linq to SQL I can use FirstOrDefault to return null if the query yields no results...is there any reason why this isn't supported?

Thanks

the 'Default' is misleading.

var q= from c in metaData.Customer.Where(c=>c.Country=="UK").FirstOrDefault() join o in metaData.Order on ....

what to do there? Result in 'null' ? What if I have a nested scalar... what to do there?

So 'OrDefault' variants work the same as First etc. (described in the doc).

Now back to your query. It shouldn't throw up in an exception. I'll check it out.

(edit). Ok this is a bug in LLBLGenProProviderBase.TResult IQueryProvider.Execute<TResult>(LinqExpression expression)

it always assumes there's a value. It should check if there's a value. Will fix it.

Ah right, I assumed that First was supposed to throw an exception (as Linq2Sql throws too) while FirstOrDefault should returns null.

Jez wrote:

Ah right, I assumed that First was supposed to throw an exception (as Linq2Sql throws too) while FirstOrDefault should returns null.

That's in theory a great idea, but in practise it doesn't work => If the 'First' is a nested query, you can't throw an exception. It's the same as with 'Single'. Single can't determine if the set is exactly 1 element if the Single query becomes a nested query.

First / FirstOrDefault now both return null in the query you showed. I can't find a requirement in the First() documentation that it should throw an exception if there aren't any values.