DataAccessLayer.DataBase.GetRolesOfAccounts C# (CSharp) Method

        public Dictionary<Guid, string[]> GetRolesOfAccounts()
        {
            string queryString = "SELECT [dbo].[UsersRoles].AccountId, [dbo].[Roles].Name " +
                                 "FROM[dbo].[Roles], [dbo].[UsersRoles] " +
                                 "WHERE[dbo].[Roles].RoleId = [dbo].[UsersRoles].RoleId;";
            using (SqlConnection connection = new SqlConnection(_connectionString))
            {
                var command = new SqlCommand(queryString, connection);

                connection.Open();
                var reader = command.ExecuteReader();
                var result = new Dictionary<Guid, string[]>();

                while (reader.Read())
                {
                    result.Add((Guid)reader[0], ((string)reader[1]).Split(','));
                }
                return result;
            }
        }