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Why does LINQ to Entities not support SingleOrDefault()?

Answer 1

+1 A:

I'm not sure why it was left out, but you can always roll your own.

I found a similar response to this question on MSDN, here is an implementation based off of that code.

public static TElement SingleOrDefault<TElement>
      (this IQueryable<TElement> query)
{
    if (query.Count() == 1)
        return query.First();
    else if (query.Count() == 0)
        return null;
    else
        throw new InvalidOperationException();
}


// Use it like this

Product prod = (from p in db.Product
                where p.ProductID == 711
                select p).SingleOrDefault();

Source: MSDN

KClough 2009-06-01 15:25:52

I didn't see the code you provided in that link. The implementation you've shown appears to be exactly like FirstOrDefault() - at least from my memory. SingleOrDefault() would return null if there are no results, return a single result if only one exists, or throw an exception if there is more than one result.

Ryan Versaw 2009-06-01 15:33:22

Actually, SingleOrDefault throws when there is more than one result found. That's the point of it--zero or one record must be returned; otherwise an error has occurred. From the docs: "this method throws an exception if there is more than one element in the sequence." Your version isn't correct.

Will 2009-06-01 15:34:13

Updated my implementation, thanks for the comments.

KClough 2009-06-01 15:41:43

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Why does LINQ to Entities not support SingleOrDefault()?

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