Question

I generated my entities via the DbContext generator, and added it to an API controller that uses my entities context model. The following method fails to compile though:

public IEnumerable<casino> Getcasinos()
    {
        var casinos = db.casinos.Include(c => c.city).Include(c => c.state);
        return casinos.AsEnumerable();
    }

The compiler says:

Cannot Convert Lambda Expression to Type 'String' Because It Is Not A Delegate Type

Any ideas why it is saying this? I have the System.Linq namespace imported.

Answer 1

This actually happens because of the ObjectQuery(T).Include method. This has the function signature:

public ObjectQuery<T> Include(string path);

The reason why you’re seeing that is probably because wherever you’re calling it does not have the System.Data.Entity namespace available. From the DbExtensions metadata you can see that the Include using an expression requires the System.Data.Entity namespace:

namespace System.Data.Entity
{
    [SuppressMessage("Microsoft.Naming", "CA1709:IdentifiersShouldBeCasedCorrectly", Justification = "Casing is intentional")]
    public static class DbExtensions
    {
        public static IQueryable<T> Include<T, TProperty>(this IQueryable<T> source, Expression<Func<T, TProperty>> path) where T : class;
        public static IQueryable<T> Include<T>(this IQueryable<T> source, string path) where T : class;
        public static IQueryable Include(this IQueryable source, string path);
    }
}

If you include the System.Data.Entity namespace, the error will resolve.