System.Nullreferenceexception: Undefined object reference for an instance of an object

Question

I am developing a project in Asp.net, where I am trying to carry out this insertion in the bank. However when I try to perform this command, I end up stating this error message: "System.Nullreferenceexception: Object reference not set to an instance of an object."

[WebMethod]
public void InsertUsuario(string usuario, string senha, string nome, string dtnasc, string fone, string email, int oab, string endereco, string bairro, string cep, int codcidade, string cpf, string cnpj)
{
            using (SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString))
            {
                string chav = "asfasdf";
                DateTime dateFromString = DateTime.Parse(dtnasc, System.Globalization.CultureInfo.InvariantCulture);
                SqlCommand command = new SqlCommand("INSERT Into Usuarios (IdUsuario, Usuario, Senha, Nome, Chave, DtNasc, Fone, Email, OAB, Endereco, Bairro, CEP, CodCidade, CPF, CNPJ) VALUES ((Select MAX(idusuario)+1 from Usuarios), '" + usuario + "', '" + senha + "', '" + nome + "', '" + chav + "', '"+dateFromString+"', '" + fone + "', '" + email + "', " + oab + ", '" + endereco + "', '" + bairro + "', '" + cep + "', " + codcidade + ", '" + cpf  + "','"+cnpj+"')");
                Console.WriteLine(dateFromString.ToString());
                conn.Open();
                command.ExecuteNonQuery();

            }
}

This is the bank created:

Create table Usuarios (
IdUsuario              int  not null,
Usuario                varchar(30) not null,
Senha                  varchar(30) not null,
Nome                   varchar(50) not null,
Chave                  varchar(18) not null,
DtNasc                 date null,
Fone                   varchar(15) not null,
Email                  varchar(70) null,
OAB                    int null,
Endereco               varchar (100) null,
Bairro                 varchar (80) null,
CEP                    varchar (9) null,
CodCidade              int null,
CPF                    varchar (20) null,
CNPJ                   varchar (20) null
primary key (IdUsuario)
)

Error message:

System.InvalidOperationException: ExecuteNonQuery: propriedade Connection não foi inicializada. em System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async) em System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(Tas‌​kCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry) em System.Data.SqlClient.SqlCommand.ExecuteNonQuery() 

Answer 1

You are not assigning the connection to command,

try to do so:

string sql = @"INSERT Into Usuarios (IdUsuario, Usuario, Senha, Nome, Chave, DtNasc, Fone, Email, OAB, Endereco, Bairro, CEP, CodCidade, CPF, CNPJ) VALUES ((Select MAX(idusuario)+1 from Usuarios), '" + usuario + "', '" + senha + "', '" + nome + "', '" + chav + "', '"+dateFromString+"', '" + fone + "', '" + email + "', " + oab + ", '" + endereco + "', '" + bairro + "', '" + cep + "', " + codcidade + ", '" + cpf  + "','"+cnpj+"')";


string chav = "asfasdf";
DateTime dateFromString = DateTime.Parse(dtnasc, System.Globalization.CultureInfo.InvariantCulture);
SqlCommand command = new SqlCommand(sql, conn);
Console.WriteLine(dateFromString.ToString());
conn.Open();
command.ExecuteNonQuery();