public Task <TUser> FindByIdAsync(long userId) { //if (long.IsNullOrEmpty(userId)) //{ // throw new ArgumentException("Null or empty argument: userId"); //} TUser result = IdentityUserRepository.GetByUserID(userId) as TUser; if (result != null) { return(Task.FromResult <TUser>(result)); } return(Task.FromResult <TUser>(null)); }