howt to Include related entities with filter condition using AsExpandable

I want to include related entities with some filter condition. Is this possible ?? I don't want to write projection query for this. So I was trying to achieve this by below code...... but it's not working.

My Domain Object

public class UserRef : BaseModel
{
    public static readonly System.Linq.Expressions.Expression<Func<UserRef, ICollection<UserNewsLetterMap>>> UserNewsLetterExp =
        UserNewsLetterExp => UserNewsLetterExp.UserNewsLetterMaps;

    public UserRef()
    {
        UserNewsLetterMaps = new HashSet<UserNewsLetterMap>();
    }

    public int UserId { get; set; }

    public string UserName { get; set; }

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public virtual ICollection<UserNewsLetterMap> UserNewsLetterMaps { get; set; }

}

My Repository code

var user = this._context.UserRefs.AsExpandable()
            .Include(u => UserRef.UserNewsLetterExp.Invoke(u).Where(news => news.Subscribe).Select(news => news.DocTypeRef))
            .SingleOrDefault(u => u.UserName == userName);

What is the best practics or best solution for this?

Thanks in advance :)

As of now I found 2 solution for my problem 1. Projection query

var result = db.UserRef
.Select(p => new
{
    User= p,
    UserNewsLetterMaps = p.UserNewsLetterMaps.Where(c => c.Subscribe == true)
})
.ToList();

2. Load related entity using eager loading.

   _context.Entry(user).Collection(u => u.UserNewsLetterMaps) .Query().Where(news => news.Subscribe) .Select(news => news).Include(news => news.DocTypeRef) .Load();