The following validation checks whether an entry is a positive number.
if (Q[i] < 0) {
Console.WriteLine("Digite um número positivo!");
goto Start;
}
Just like this check, if nothing was typed, the program would only return to the "Start" without displaying an error.
That is, how do I check if the entry is empty because the user did not enter anything?
Console.Write("Informe um valor: ");
string value = Console.ReadLine();
if (String.IsNullOrEmpty(value))
{
Console.WriteLine("O usuário não informou valor");
goto Start;
}
else
{
Console.WriteLine("O valor é: {0}", s);
}
Note that I used the Boolean method String.IsNullOrWhiteSpace because it indicates whether a specified string is null, empty, or consists of only whitespace characters. So if the variable has no character, it will then enter the first if , stating that the user did not enter any value.
I hope I have helped.