public async Task <List <Speciality> > GetSpecialitiesAll()
        {
            List <Speciality> results = null;
            var filter = new BsonDocument("Code", new BsonDocument("$ne", ""));

            results = await Specialities.Find <Speciality>(filter).ToListAsync();

            if (results != null)
            {
                return(results);
            }
            else
            {
                return(null);
            }
        }
        /*public async Task<User> GetUsersAsync(string email, string pass)
         * {
         *
         *  List<User> results = null;
         *  var filter = new BsonDocument("$and", new BsonArray{
         *
         *   new BsonDocument("Email",new BsonDocument("$eq", email)),
         *   new BsonDocument("Password", pass)
         *  });
         *  results = await Users.Find<User>(filter).ToListAsync();
         *  if (results != null)
         *      return results.FirstOrDefault();
         *  else return null;
         * }*/

        // получаем один документ по id

        /*public async Task<User> GetUser(string id)
         * {
         *  return await Users.Find(new BsonDocument("_id", new ObjectId(id))).FirstOrDefaultAsync();
         * }*/
        public async Task <Speciality> GetSpecialityCode(string code)
        {
            List <Speciality> results = null;
            var filter = new BsonDocument("Code", new BsonDocument("$eq", code));

            results = await Specialities.Find <Speciality>(filter).ToListAsync();

            if (results != null)
            {
                return(results.FirstOrDefault());
            }
            else
            {
                return(null);
            }
        }