Need help in querying many to many relationship.

Hi,

Need help in querying many to many relationship.

I have 3 tables
1] Games

GameID	Game Title
1	FIFA 10
2	Halo 3
3	DIRT

2] Platforms

PlatformID	PlatformName
1	XBox 360
2	PS3
3	PSP
4	Wii

3] GamePlatforms

GameID	PlatformID
1	1
1	2
1	3
2	2
2	3

Now i need to query All Games in PlatformID X

POCO

public class Game
    {
        [Key]
        public int GameId { get; set; }


        [Column("GameTitle")]
        public string Title { get; set; }
 
 public virtual ICollection Platforms { get; set; }
    }   

 public class Platform
    {
        [Key]
        public int PlatformId { get; set; }

        [Column("Platform")]
        public string Name { get; set; }

 public virtual ICollection Games { get; set; }
}

// Mapping

modelBuilder.Entity()
            .HasMany(u => u.Platforms)
            .WithMany()
            .Map(a =>
            {
                a.ToTable("GamePlatforms");
                a.MapLeftKey("GameId");
                a.MapRightKey("PlatformId");
            });

Service Layer

 public IEnumerable Search(int platformId, string gameName)
        {
            Platform _platform = platformRepository.Get(platformId);
            var predicate = PredicateBuilder.True();
            predicate = predicate.And(mg => mg.Game.Platforms.Contains(_platform)).And(mg => mg.Game.Title == gameName).Or(mg => mg.Game.Title.Contains(gameName));


            return repository.GetMany(predicate);          
        }

Data Layer

public virtual IEnumerable GetMany(Expression> where)
        {
            return _dbSet.Where(where).ToList();
        }  


throws an error Unable to create a constant value of type 'XXXX.BO.Platform'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.

Please help me to solve the problem.

Thanks inadvance
Satish