DbIsNullExpression exception in linq to EF4 query

Question

I have writed linq EF4 query, but it failed with exception The argument to "DbIsNullExpression must refer to a primitive, enumeration or reference type." The query written bellow:

from listing in ctx.listingSource
join listingFile in ctx.ListingFiles
         .Where(x => companyIds.Contains(x.CompanyID.Value))
         .GroupBy(x => x.ListingID)
         .Select(x => new { ListingId = x.Key, Count = x.Count() }) on listing.ListingID equals listingFile.ListingId into listingFilesJoined
from listingFileJoined in listingFilesJoined.DefaultIfEmpty()
select new ListingDTO
{
    fileCount = listingFileJoined == null ? 0 : listingFileJoined.Count,
}

How can I resolve this issue without creating class instead anonymous type ?

Answer 1

There are no way to select data without creating concrete type =\ There is fix bellow:

.Select(x => new ConcreteType { ListingId = x.Key, Count = x.Count() }) 

Maybe this answer help someone.

Answer 2

fileCount = (int?)listingFileJoined.Count ?? 0