C# Recursion in ASP.NET Web Application: displaying numbers from static method in listbox

Question

I'm trying to learn recursion in C#. I am able to do a simple count down in a console application, but I am not sure how to do the same thing in an ASP.NET web application. I would like to display the result in a listbox, but I cannot access the listbox in a static function.

Here is what I have for my console application:

    static void Main(string[] args)
    {
        int startInt = 100;
        countDown(startInt);
        Console.ReadLine();

    }
    public static void countDown(int integer)
    {
        if (integer == 1)
        {
            Console.WriteLine(integer);
        }
        else 
        {
            Console.WriteLine(integer);
            integer--;
            countDown(integer);
        }
    }

Any help on getting this to work in a web application that will display the numbers in a listbox?

Take a look at my answer to a previous question which gives an example of using recursion in a C# ASP.NET application stackoverflow.com/a/9753547/459517 — Robbie
– Robbie, Commented Apr 21, 2013 at 20:16

Wiktor Zychla · Accepted Answer · 2013-04-21 16:21:53Z

1

You shouldn't need to keep it static, since you're no longer calling it from a static function. Using a countDown function like this one

public void countDown(int integer)
{
    if (integer > 0)
    {
        ListBox1.Items.Add(integer.ToString());
        integer--;
        countDown(integer);
    }
}

should work just fine. I tested it out by putting

int startInt = 100;
countDown(startInt);

in the Page_Load method, and the ListBox displays as expected.

edited Apr 21, 2013 at 16:21

Wiktor Zychla

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answered Apr 20, 2013 at 22:28

Mike Precup

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2 Comments

zkanoca Over a year ago

The problem is about accessing objects from a static method. So your answer is not suitable, I guess.

Wiktor Zychla Over a year ago

What an unfortunate duplication of code. It should really be rewritten.

zkanoca · Accepted Answer · 2013-04-20 22:37:49Z

0

I am not sure if there are performance issues, or better solutions. But this works and could be a good example for undrstanding recursion.

protected void Page_Load(object sender, EventArgs e)
{
    int startInt = 100;
    form1.Controls.Add(countDown(startInt, new ListBox()));
}

public static ListBox countDown(int integer, ListBox lb)
{
    ListItem li = new ListItem();

    if (integer > 0)
    {
        li.Text = integer.ToString();
        lb.Items.Add(li);

        integer--;
        countDown(integer, lb);
    }
    return lb;

}

edited Apr 20, 2013 at 22:37

answered Apr 20, 2013 at 22:35

zkanoca

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