How should I deal with mistakes?

Question

Read a vector A with 12 elements. The vector must accept only the input of values that are divisible by 2 or 3. The input of values in the vector must be validated by the program and not by the user. The program must show on the screen the numbers inserted in the vector.

Note: Use error handling/exception routines.

And my code is exactly this:

        static void Main(string[] args)
    {
        string aux; // variavel auxiliar que ira receber o que o usuario digitar.
        int valor;
        int[] vetor = new int[12];

        for (int i = 0; i < 12; i++)
        {
            aux = Console.ReadLine();
            valor = int.Parse(aux);

            Console.WriteLine("Digite um valor para o vetor");

            while ((valor%2!=0) && (valor%3!=0))
            {
                Console.WriteLine("Apenas valores divisíveis por 2 e 3!");
                aux = Console.ReadLine();
                valor = int.Parse(aux);
            }
            vetor[i] = valor;
        }

        imprimeVetor(vetor);

        Console.ReadKey();
             


      }

    static void imprimeVetor(int[] vetor)
    {

        for (int i = 0; i < 12; i++)
        {

  
                Console.Write(vetor[i] + " - ");
                         
            
        }

    }

How to work with these error treatments. I have not used methods try-catch, should? I already check what is important in my while.

Answer 1

Avoid exceptions as much as possible. Only use when it makes a lot of sense. Exception is the most poorly used feature of programming nowadays. People don’t know when to launch, let alone when to capture. Interestingly, they abuse the exception, but practically never create their own exception that would make more sense. I mean, people wear something they don’t understand and that’s why it only comes out wrong.

The only change you should make is to use the TryParse() to ensure that the data entered is valid. Otherwise I gave an organized, modernized and simplified in the code.

using static System.Console;

public class Program {
    public static void Main(string[] args) {
        var vetor = new int[12];
        var i = 0;
        while (i < 12) {
            WriteLine("Digite um valor para o vetor");
            if (int.TryParse(ReadLine(), out var valor)) {
                WriteLine("Você digitou o caractere de forma inválida. Por favor, digite apenas númeris inteiros!");
                continue;
            }
            if (valor % 2 != 0 && valor % 3 != 0) {
                WriteLine("Apenas valores divisíveis por 2 e 3!");
                continue;
            }
            vetor[i++] = valor;
        }
        imprimeVetor(vetor);
    }
    static void imprimeVetor(int[] vetor) {
        foreach (var item in vetor) Write($"{item} - ");
    }
}

Behold working in the ideone. And in the .NET Fiddle. Also put on the Github for future reference.

This version works on C# 7, the code in Coding Ground works on C# 6, do not recommend using previous versions.

Answer 2

I ended up solving the "problem". I thought I should use a custom Exception to treat divisible numbers. In case, I used catch and Try just to make sure that the user will report only numbers. Follow the code snippet:

            Console.WriteLine("Digite um valor para o vetor");
            try
            {
                aux = Console.ReadLine();
                valor = int.Parse(aux);

            }
            catch
            {
                Console.WriteLine("Você digitou o caractere de forma inválida. Por favor, digite apenas númeris inteiros!");
                aux = Console.ReadLine();
                valor = int.Parse(aux);
            }

Answer 3

Preventing user errors does not mean you cannot have syntax errors for example.

Here was what I would do:

static void Main(string[] args)
{
    string aux; // variavel auxiliar que ira receber o que o usuario digitar.
    int valor;
    int[] vetor = new int[12];
    try{

        for (int i = 0; i < 12; i++)
        {
            aux = Console.ReadLine();
            valor = int.Parse(aux);

            Console.WriteLine("Digite um valor para o vetor");

            while ((valor%2!=0) && (valor%3!=0))
            {
                Console.WriteLine("Apenas valores divisíveis por 2 e 3!");
                aux = Console.ReadLine();
                valor = int.Parse(aux);
            }
            vetor[i] = valor;
        }
        imprimeVetor(vetor);
    }
    catch (Exception ex)
    {
        Console.WriteLine("ERRO: {0}", ex.Message);
    }
    Console.ReadKey();
    }

static void imprimeVetor(int[] vetor)
{
    try{
        for (int i = 0; i < 12; i++)
        {
                Console.Write(vetor[i] + " - ");
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("ERRO: {0}", ex.Message);
    }
}