Question

I am trying to use LINQ/LAMBDA access a property

List<Latest> latestBooks = DataContext.Session.Query<Book>().Where(x=> x.Enabled == "True" ).Select(x => new Latest(x.Title,x.Author)).Take(10).ToList();

But there is another property defined in the Book class that look like this:

public virtual string FrontEndLink { get { return string.Format("http://myurl/{0}", Filename); } }

When I try this

List<Latest> latestBooks = DataContext.Session.Query<Book>().Where(x=> x.Enabled == "True" ).Select(x => new Latest(x.FrontEndLink)).Take(10).ToList();

The code breaks and give me an error:

Could not resolve property: Quote((x, ) => (x.Id)), ), Quote((x, ) => (new Latest(x.FrontEndLink, ))), ), p1, )]

Answer 1

LINQ to Entities is trying to convert everything before the ToList into SQL – and it won’t be able to do that with your FrontEndLink property. You want to do that bit in LINQ to Objects, but after filtering to only 10 results. So I’d use:

var latestBooks = DataContext.Session.Query<Book>()
                             // Do the first bit in the database
                             .Where(x=> x.Enabled == "True")
                             .Take(10)
                             // Do the rest in LINQ to Objects
                             .AsEnumerable()
                             .Select(x => new Latest(x.FrontEndLink))
                             .ToList();