How do I create a dynamically sized array, or re-size an array in c#?

Question

I need to know how to dynamically re-size an array in C#. In the method that I have written below, I need to be able to return an array that only contains the numbers that were input by the user up to 8 numbers. So if the user decides they only want to enter 3 numbers, the array should only contain 3 numbers, not 8.

Now I know that an array needs to include a size when instantiated. So how do I get around this without using a list? Is there a way to re-size the array after the loop is done?

Thanks in advance.

        static int[] fillArray()
    {
        int[] myArray;
        myArray = new int[8];
        int count = 0;
        do
        {
            Console.Write("Please enter a number to add to the array or \"x\" to stop: ");
            string consoleInput = Console.ReadLine();
            if (consoleInput == "x")
            {
                Array.Resize(ref myArray, count);
                return myArray;
            }
            else
            {
                myArray[count] = Convert.ToInt32(consoleInput);
                ++count;
            }

        } while (count < 8);

        Array.Resize(ref myArray, count);
        return myArray;

    }

WHy not use a resizable collection type like ArrayList or List? — BJ Safdie
– BJ Safdie, Commented Mar 1, 2011 at 0:27
A List<> is nothing but an array with a Count and a Capacity property. Implement your own. — Hans Passant
– Hans Passant, Commented Mar 1, 2011 at 1:01

Rob · Accepted Answer · 2011-03-01 00:26:09Z

7

You could use a List<int> during your method logic and then return myIntList.ToArray();

answered Mar 1, 2011 at 0:26

Rob

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9 Comments

Vlad Over a year ago

... or even make fillArray return IEnumerable<int>.

Tharkis Over a year ago

Yes, I could do that. But I want to accomplish this without using a list.

Rob Over a year ago

@antisanity - lol I was thinking that too - it's the only time Occam's Razor goes out the window...

Tharkis Over a year ago

Well yes because that is what the homework assignment requires, otherwise I'd have just used a list and been done with the assignment 3 days ago. I'm just stumped as how to do this otherwise. I asked the teacher why I'd ever want to do this in real life and he replied " An array allows you to have random access to any element. A list doesn't allow that, unless each element is indexed, in which case it is probably implemented as an array." Sooo I'm stuck.

Tharkis Over a year ago

Also I do want to point out, I'm not asking you to fix my code, or write it for me. I just need someone to point me in the right direction and maybe tell me why I should do it that way. If I don't figure it out soon, I'm just going to go with creating a list and converting it to an array before I return it method.

|

Ian Dallas · Accepted Answer · 2011-03-01 00:27:36Z

Typically for this type of application you'll want to use a List. And if you really need an array you can use the ToArray method but reconsider if an array is really what you want. Usually a List is used for a dynamically sized collection instead of an array.

You could always modify your code as follows:

static int[] fillArray()
{
    List<int> list = new List<int>();

    do
    {
        Console.Write("Please enter a number to add to the array or \"x\" to stop: ");
        string consoleInput = Console.ReadLine();

        if (consoleInput == "x")
        {
            return list.ToArray();
        }
        else
        {
            list.Add(Convert.ToInt32(consoleInput));
        }

    } while (count < 8);

    return list.ToArray();
}

But as I mentioned before, really reconsider changing your method to return a List and use the List in your calling code.

dskut · Accepted Answer · 2011-03-01 08:17:15Z

0

Well you could implement your own method accepting the array and new size as parameters that would create new array, deep-copy the elements and then assign to your array. Array.Resize() does the same, you can watch it with disassembler

answered Mar 1, 2011 at 8:17

dskut

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