Dynamically Create an Array in C#

Question

How can I dynamically create an array in C#?

What do you mean by that? Please show some pseudocode of what you are trying. — shahkalpesh, May 19 '09 at 05:51

score 24 · Answer 1 · answered May 19 '09 at 05:56

24

I'd like to add to Natrium's answer that generic collections also support this .ToArray() method.

List<string> stringList = new List<string>();
stringList.Add("1");
stringList.Add("2");
stringList.Add("3");
string[] stringArray = stringList.ToArray();

answered May 19 '09 at 05:56

Gerrie Schenck

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1

As a note, they support ToArray() because internally, list is just plain using an immutable array and growing it with new allocations as needed. – Dec 07 '14 at 10:50

score 8 · Answer 2 · answered May 19 '09 at 05:50

8

First make an arraylist. Add/remove items. And then ArrayList.ToArray()

And there is your array!

answered May 19 '09 at 05:50

Natrium

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score 7 · Answer 3 · edited Nov 11 '15 at 16:49

7

object foo = Array.CreateInstance(typeof(byte), length);

edited Nov 11 '15 at 16:49

SgtOJ

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answered May 19 '09 at 05:55

Matthew Flaschen

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score 7 · Answer 4 · answered May 19 '09 at 06:52

Ok so array initialisation gets me every single time. so I took 10 minutes to do this right.

    static void Main(string[] args)
    {
        String[] as1 = new String[] { "Static", "with", "initializer" };
        ShowArray("as1", as1);

        String[] as2 = new String[5];
        as2[0] = "Static";
        as2[2] = "with";
        as2[3] = "initial";
        as2[4] = "size";
        ShowArray("as2", as2);

        ArrayList al3 = new ArrayList();
        al3.Add("Dynamic");
        al3.Add("using");
        al3.Add("ArrayList");
        //wow! this is harder than it should be
        String[] as3 = (String[])al3.ToArray(typeof(string));
        ShowArray("as3", as3);

        List<string> gl4 = new List<string>();
        gl4.Add("Dynamic");
        gl4.Add("using");
        gl4.Add("generic");
        gl4.Add("list");
        //ahhhhhh generic lubberlyness :)
        String[] as4 = gl4.ToArray();   
        ShowArray("as4", as4);
    }

    private static void ShowArray(string msg, string[] x)
    {
        Console.WriteLine(msg);
        for(int i=0;i<x.Length;i++)
        {
            Console.WriteLine("item({0})={1}",i,x[i]);
        }
    }

Bojan Resnik · Accepted Answer · 2009-05-19T08:51:02.330

2

You can also use the new operator just like with other object types:

int[] array = new int[5];

or, with a variable:

int[] array = new int[someLength];

edited May 19 '09 at 08:51

answered May 19 '09 at 06:10

Bojan Resnik

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This is not quite dynamic is it? – Gerrie Schenck May 19 '09 at 06:13
Why not? You can use a variable instead of a literal 5 there. – Bojan Resnik May 19 '09 at 08:50
once defined, you will need to re-initiate the array in order to add more than 5 items – Natrium May 19 '09 at 09:44
3

That's correct - however, the OP asked about dynamic creation of arrays, not necessarily about the ability to dynamically grow an array. – Bojan Resnik May 19 '09 at 10:55

score -1 · Answer 6 · edited Feb 15 '16 at 18:52

-1

int[] array = { 1, 2, 3, 4, 5};

for (int i=0;i<=array.Length-1 ;i++ ) {
  Console.WriteLine(array[i]);
}

edited Feb 15 '16 at 18:52

Jan Doggen

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answered Feb 15 '16 at 18:30

sina rezaei

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score -1 · Answer 7 · answered May 19 '09 at 06:18

-1

Use generic List or ArrayList.

answered May 19 '09 at 06:18

blitzkriegz

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Dynamically Create an Array in C#

7 Answers7