public class Users
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string TwoName { get; set; }
        public string LastName { get; set; }
        public string Login { get; set; }
        public string Password { get; set; }
        public string Telephone { get; set; }
        public string Position { get; set; }
        public int Group { get; set; }
        public int OvdId { get; set; }
        public virtual Ovd Ovd { get; set; }
    }

    
public class Ovd
    {
        public int Id { get; set; }
        public string OvdName { get; set; }

        public virtual ICollection<Users> Ovdd { get; set; }

        public Ovd()
        {
            Ovdd = new List<Users>();
        }
        public override string ToString()
        {
            return OvdName;
        }
    }

List<Ovd> ovds = db.Ovds.ToList();
            // Список отделов
            AddF.OvdBox.DataSource = ovds;
            AddF.OvdBox.ValueMember = "OvdId";
            AddF.OvdBox.DisplayMember = "OvdName";