Error handling exceptions - "Object reference not set to an instance of an object"

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Error handling exceptions - "Object reference not set to an instance of an object"

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#1 by (0 votes)

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public String IdentificarAcessoDAL(FuncionarioDTO acesso)
    {
        try
        {
            conexao.cmd.Connection = conexao.conexao;
            string recuperar = "SELECT CARGO.NOME_CARGO FROM LOGIN INNER JOIN FUNCIONARIO ON FUNCIONARIO.CPF_FUNCIONARIO = LOGIN.CPF_FUNCIONARIO INNER JOIN CARGO ON CARGO.ID_CARGO = FUNCIONARIO.ID_CARGO WHERE LOGIN.USUARIO_LOGIN = '" + acesso.User + "' AND LOGIN.SENHA_LOGIN = '" + acesso.Password + "'";
            conexao.cmd.CommandText = recuperar;

            conexao.conexao.Open();
            return funcionarioDTO.Funcao = conexao.cmd.ExecuteScalar().ToString();
        }
        catch (Exception erro)
        {
            throw erro;
        }
        finally
        {
            conexao.conexao.Close();
        }
    }

Whenever I type the correct information it runs the application perfectly, but when it does not find in the database, it simply to run the program and displays the following error:

The program searches for the official position, using the login and the password, and this error only appears when the login and / or password is incorrect, otherwise it works perfectly.

mysql c# .net nullpointerexception

asked by anonymous 21.10.2018 / 07:51

1 answer

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score 0 · Accepted Answer

public String IdentificarAcessoDAL(FuncionarioDTO acesso) {
    try {
        conexao.cmd.Connection = conexao.conexao;
        conexao.cmd.CommandText = "SELECT CARGO.NOME_CARGO FROM LOGIN INNER JOIN FUNCIONARIO ON FUNCIONARIO.CPF_FUNCIONARIO = LOGIN.CPF_FUNCIONARIO INNER JOIN CARGO ON CARGO.ID_CARGO = FUNCIONARIO.ID_CARGO WHERE LOGIN.USUARIO_LOGIN = '" + acesso.User + "' AND LOGIN.SENHA_LOGIN = '" + acesso.Password + "'";
        conexao.conexao.Open();
        return funcionarioDTO.Funcao = conexao.cmd.ExecuteScalar().ToString();
    } finally {
        conexao.conexao.Close();
    }
}

Ready, simple.

The code is still not good. Surely this connection control is something badly done and this would need to be fixed, but it is not the focus of the question. The architecture of this application is certainly a source of problems you are having and will have in the future, I would simplify this.

The solution was simple because it was doing something unnecessary there. Why catch an exception to do anything? Exceptions exist to propagate the error, only capture when you know what to do with it and solve it properly, it does not make sense to capture to do anything.

I'd rather do it as soon as it's simpler to manage:

public String IdentificarAcessoDAL(FuncionarioDTO acesso) {
    using (var connection = new SqlConnection(connectionString)) {
        var command = new SqlCommand("SELECT CARGO.NOME_CARGO FROM LOGIN INNER JOIN FUNCIONARIO ON FUNCIONARIO.CPF_FUNCIONARIO = LOGIN.CPF_FUNCIONARIO INNER JOIN CARGO ON CARGO.ID_CARGO = FUNCIONARIO.ID_CARGO WHERE LOGIN.USUARIO_LOGIN = '" + acesso.User + "' AND LOGIN.SENHA_LOGIN = '" + acesso.Password + "'", connection);
        command.Connection.Open();
        command.ExecuteNonQuery();
    }
}

I placed GitHub for future reference .

Lie, I'd make it simpler yet, but it depends on a specific architecture, it's not the focus of the question and it's too broad to put into an answer.

ATTENTION! I did not fix the serious security problem that has in the application, I focused only on the specific problem. See the correct one . Another example .