Variable with unassigned value within a "for" loop

Question

    int i;
    string cpf;
    cpf = "11111111111";
    DbConnection cnx = ADO_Utils.GetConnection();
    DbCommand cmd = ADO_Utils.GetComando(cnx);
    cmd.CommandType = CommandType.Text;
    for (i = 1; i < Convert.ToInt32(txbQtde.Text); i++) ;
    {
        string query;
        query = "insert into tblAcordoParcel (txtCPF, intParcela, dblValorParcel, dtVencimento, blnBaixada) ";
        query = query + "Values (  " + "'" + cpf + "',";
        query = query + i + ",";
        query = query + "" + txbParcel.Text + ",";
        query = query + "'" + txbDt.Text + "',";
        query = query + "0"+ ")";
        try
        {
            cmd.CommandText = query;
            cmd.ExecuteNonQuery();
        }
        catch (Exception ex)
            {
                throw ex;
            }

When executing this code, the variable i assumes the value typed on the screen and not the number 1 I declared within the for.

Answer 1

The mistake is that the for is not running, it is being shut down even before starting, after all right at the beginning of it there is already a ; that closes it. The correct thing would be to have a block of commands next, like this:

var cpf = "11111111111"; //se não for só um teste não precisa da variável
DbConnection cnx = ADO_Utils.GetConnection();
DbCommand cmd = ADO_Utils.GetComando(cnx);
cmd.CommandType = CommandType.Text;
for (var i = 1; i < Convert.ToInt32(txbQtde.Text); i++) { // <==== note que não tem o ;
    cmd.CommandText = @"insert into tblAcordoParcel (txtCPF, intParcela, dblValorParcel, 
dtVencimento, blnBaixada) Values (@cpf, @i, @parcel, @dt, 0)";
    cmd.Parameters.AddWithValue("@cpf", cpf);
    cmd.Parameters.AddWithValue("@i", i);
    cmd.Parameters.AddWithValue("@parcel", txbParcel.Text);
    cmd.Parameters.AddWithValue("@dt", txbDt.Text);
    cmd.ExecuteNonQuery();

I put in the Github for future reference.

Note that I made some changes.

I pulled the exception because she wasn’t doing anything useful. If you don’t have something useful to do with the exception, don’t capture it.

I simplified putting the statement and assignment on the same line, there is no reason to do in separate lines. In some cases I used the var which also simplifies.

And mostly I used the right command to mount the query safely. What was being done was a recklessness.

Use a guy double for monetary value is another temerity.

There are other things that seem weird, but as I am not seeing the whole I will not pronounce. One of them is the use of hungarian notation in column names. Have other.

If the types of dblValorParcel and dtVencimento are numeric and date, probably need to make a conversion before using it, since what comes from outside comes as string. If any conversion goes wrong for some reason (a text that does not produce a number, for example), there will be an exception and it will be a programming error. This is even true for the Convert already existing. Ideally it would be to treat this differently and avoid the exception, but it is another matter.