由于 StackOverflowExeption 导致进程终止 - C#

Question

I have this problem with my code I cant fix.

I am making a quiz, but the questions mustnt be asked twice so I avoided that, but when it runs out of options it crashes.

It also could be the code after it, but I dont think so.

Here is my code:

private static void chooseQuestion()
{
    Random randomQuestion = new Random();

    int returnValue = randomQuestion.Next(1, 3);

    switch (returnValue)
    {
        case 1:
            if (randomValues.questionOneChosen != 1)
            {
                questionOne();
            }else
            {
                chooseQuestion();
            }
            break;
        case 2:
            if (randomValues.questionTwoChosen != 1)
            {
                questionTwo();
            }else
            {
                chooseQuestion();
            }
            break;
    }

    endQuiz();
}

and here is what is after it:

private static void endQuiz()
{
    Console.Clear();
    Console.WriteLine();
    text.centered("You completed the QUIZ, well done!");
    Console.WriteLine();
    text.centeredWrite("Press ENTER to go back to the menu");
    string input = Console.ReadLine();
    if (input == "")
    {
        Menu.main();
    }else
    {
        endQuiz();
    }
}

If you need more code to help me, please ask me.

Thanks in advance!

Answer 1

This is never getting set.

randomValues.questionOneChosen

So whatever it is, if it's not 1 or 2 the method is going to call itself again. It's probably always zero.

Answer 2

Your chooseQuestion method's logic goes like this:

a. Pick a 1 or 2, randomly
b. If 1, and I haven't asked question 1 yet, show question 1
c. if 1, and I have asked question 1, go to step (a)
d. repeat (b) and (c) for question 2
...

once you answer both questions, you try to get another random question. But there are no more questions available. So you recurse into an exception.

Don't write your logic this way. Use a collection, and remove the item from the collection after you've shown that question. When the collection is empty, you're done.

Answer 3

A StackOverflowException on StackOverflow, nice! Does Menu.main() end up calling chooseQuestion()? When a function is called, a new entry on the stack is created with room for all its local variables and the address to return to when it returns. If a function calls itself (recursive call), its original stack entry is not released. If it calls itself often enough without returning, the stack will eventually run out of room and give this exception. Having said that, the stack is pretty big - I think the default is 1 megabyte - so you need a lot of recursive calls to exhaust it.

You've got two functions which both call themselves. If they do it often enough, you'll run out of stack space. Just replace the recursive calls with a loop. Here's your first function:

private static void chooseQuestion() 
{    
    bool endQuizChosen = false;
    while ( !endQuizChosen ) {
        Random randomQuestion = new Random();
        int returnValue = randomQuestion.Next(1, 3);  
        // ... the rest of the function ...
        endQuizChosen = endQuiz();
    }
}

and edit endQuiz() to not call itself but to return true if user wants to stop and false if they want to go on.