System.NullReferenceException. How to include fields from another table?

Question

Friends, I had a table Pessoa that contained a lot of user information. I decided to create a table Aluno to separate the information. My tables are like this:

Person: Cod, Nome, Email, Senha
Pupil: Cod, Status, Data_Registro, PessoaId

I am trying to get a list of requests from the connected user. However, my table Pedidos has a key to the table Alunos, not for the table Pessoa. The information of Aluno is null. How can I include it in the table Pessoa?

Error:

System.NullReferenceException: 
  'Object reference not set to an instance of an object.'

LojaVirtual.Models.pessoa.aluno.get retornou null.

Pedidocontroller.Cs

public IActionResult Index(int pagina)
{
    pessoa pessoa = _loginPerson.GetPessoa();
    var requests= _requestRepository.ObterTodosPedidoPessoa(pagina, pessoa.aluno.Cod);

    return View(pedidos);
}

Médoto Getpessoa()

public pessoaGetPessoa()
{
    //Deserializar
    if( _sessao.Existe(Key)) {
        string pessoaJSONString = _sessao.Consultar(Key) ;
        return JsonConvert.DeserializeObject<pessoa>(pessoaJSONString);

    }
    else
    {
        return null;
    }
}

Method Consult

public string Consultar(string Key)
{
    return _context.HttpContext.Session.GetString(Key);
}

I thank you for any comment!

Answer 1

If I understand correctly, the problem is in the fact of having a Pessoa but not having a Aluno, since the key to Pedidos is connected to the Aluno. The only way I can see to make that call would be to access the property Cod which is present in both entities, if they have the same value for the records in the tables Aluno and Pessoa:

var requests = _requestRepository.ObterTodosPedidoPessoa(pagina, pessoa.Cod);

If the record Cod is not the same for Aluno and Pessoa, see as a solution the "direct link" between Pessoa and Pedido, since, if understood correctly, there is always a Pessoa but not always this Pessoa is a Aluno.