public async Task AddToRoleAsync(T user, string roleName) { if (user == null) { throw new ArgumentNullException("user", "Parameter user cannot be null."); } if (string.IsNullOrEmpty(roleName)) { throw new ArgumentNullException("roleName", "Parameter roleName cannot be null."); } var roleId = await _roleTable.GetRoleIdAsync(roleName); if (roleId != null) { await _userRolesTable.AddUserToRoleAsync(user, (string)roleId); } }