Question

In .NET4 MVC 4 using Code First I have two classes that form a many to many relationship.
How can I write a simple LINQ query to find all Games that have at least one or more genres from a given list of genres? (i.e. Retreive all games that are of the Strategy and/or Sandbox genre)

public class Game
{
    public int ID { get; set; }
    public virtual ICollection<Genre> Genres { get; set; }
}

public class Genre
{
    public int ID { get; set; }
    public virtual ICollection<Game> Games { get; set; }
}

Please note that I am using Code First so I have no access to the abstracted join table GenreGames.

I have tried the following to find a game that contains at least one genre ID from the array gid:

var gid = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
var result = from g in unitOfWork.GameRepository.dbSet
             where (
                 from gen in unitOfWork.GenreRepository.dbSet
                 where gid.Contains(gen.ID)
                 select gen.ID
             ).Any()
             select g;

When retrieving the results

List<Game> similiarGames = result.ToList<Game>();

the following error comes up.

Unable to create a constant value of type ‘GratifyGaming.Domain.Models.Genre’. Only primitive types or enumeration types are supported in this context.

How can I get the results I want using only primitive or enumeration types? Is there a workaround?

Answer 1

Try this instead :

var test = unitOfWork.GameRepository.dbSet
                         .Where(G => G.Genres.Where(genre => 
                                     gid.Contains(genre .ID)).Count() > 0);

Good Luck !!