Question

I’m trying to validate an ID.

I have this class called ManejadorTickets in which -among others things- I call the method to validate an ID (the ID is the Cedula is something like SSN in USA).

    public void venderTicket ()
    {
        // more code...

        Console.Write("\nCedula: ");
        string cedula = Validador.validarCedula(Console.ReadLine().Trim());

        // more code...
    }

This is my validarCedula method in Validador class.

public static String validarCedula (string cedula)
        {
            // Limpiar la entrada de caracteres extraños
            cedula = cedula.Replace("-", "");
            cedula = cedula.Replace(" ", "");

            // Debe tener 11 caracteres
            if (cedula.Length != 11)
            {
                Impresor.imprimirOpExitosa(cedula.Length.ToString());
                Impresor.imprimirError("La cedula debe tener 11 digitos", "Cedula: ");
                validarCedula(Console.ReadLine().Trim());
            }

            // Todos los caracteres deben ser numeros
            char[] arrayLetras = cedula.ToCharArray();
            foreach (char c in arrayLetras)
            {
                if (NUMEROS.IndexOf(c) == -1)
                {
                    Impresor.imprimirError("Todos los caracteres deben ser numericos." +
                                            " Los guiones o espacios no se toman en cuenta.", "Cedula: ");
                    validarCedula(Console.ReadLine().Trim());

                }
            }

            return cedula;
        }

The method above eliminate hyphens and space from the input. Is also check if the input has exactly 11 characters and if all characters are numbers.

Note: NUMBERS is a constant I declared at the beginning of the class
private const string NUMEROS = "0123456789";

But when I running the program, enter a wrong value as a Cedula (to test my validation method) such as “foo”, it happens what should happens (ask for the value again). So far so good, now when I type a correct value such as 00114905656 (all numbers and 11 digits) it ask again for a value and that should not happen because the last entered value was correct.

I tried debugging my applications and I see that the method execute as it should, but when the compiler execute the statement return cedula; (last sentence in the method) it jumps to the first validarCedula(Console.ReadLine().Trim()); statement that’s the one inside the if (cedula.Length != 11) statement. And I don’t understand WHY that happens. When the return is executed the method is supposed to finish.

Answer 1

You are calling validarCedula from within itself. This is called recursion.

Try stepping through from the beginning. Look at the call-stack window.

I think you need to restructure your program a bit.

Try implementing validarCedula more like this:

static bool validarCedula(string cedula) {
   // do your string replace here
   // if it's ok, return true
   // if it's bad, return false.  
   // do not call validarCedula from here!      
}

And then do this in your vendorTicket function, so you still get it to re-prompt until it passes:

string cedula;
bool ok = false;
while (!ok) {
    Console.Write("\nCedula: ");
    cedula = Console.ReadLine().Trim();
    ok = validarCedula(cedula);
}