Entity Framework nested lambda query

Question

In Linq2Sql, it was possible to do a query such as:

using (var db = GetDataContent())
            {
                var query = from p in db.Brands
                            where p.Deleted == false
                            select new BrandImageSummary
                            {
                                BrandID = p.BrandID,
                                BrandUrl = p.BrandUrl,
                                Description = p.Description,
                                MetaDescription = p.MetaDescription,
                                MetaKeywords = p.MetaKeywords,
                                MetaTitle = p.MetaTitle,
                                BrandImageUrl = (from p2 in db.SiteImages where p2.FileTypeID == 5 && p2.ForeignID == p.BrandID && p2.Deleted == false orderby p2.Rank select p2.Filename).FirstOrDefault(),
                                Deleted = p.Deleted,
                                SupplierCode = p.SupplierCode,
                                Title = p.Title,
                                Website = p.Website
                            };

                return query.ToList();
            }

With BrandImageUrl being a nested select. Howerver in entity framework, I seem to get the error:

Unable to create a constant value of type 'SiteImage'. Only primitive types or enumeration types are supported in this context.

Is there a way to do this in entity framework?

The idea of the query is to get one brand image, if I was to join, and there was multiple images, I would get multiple rows and I do not want this.

I am using Entity Framework 5.

Thanks for your help

SLaks · Accepted Answer · 2012-08-22 13:32:36Z

1

You should create a one-to-many relation in your model classes.

You can then write

BrandImageUrl = p.BrandImages
                 .Where(i => i.FileTypeID == 5 && !i.Deleted)
                 .OrderBy(i => i.Rank)
                 .Select(i => i.FileName)
                 .FirstOrDefault()

answered Aug 22, 2012 at 13:32

SLaks

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1 Comment

user614143 Over a year ago

Thanks for this, but is there now way of doing this without setting up reference's? I'm trying to port a application to entity framework and there are lots and lots queries like that..

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