adding an element to a C# array from a text box

Question

I am struggling to add an element into an array from a text box using C# Windows Forms. hers what I have so far:

int[] id;

private void btnButton1_Click(object sender, EventArgs e)
    {
        //INSERTION SORT
        int newItem = txtAddElement.text;

        //CODE HERE TO ADD ELEMENT TO ARRAY


        //CODE BELOW THEN SORTS ARRAY INTO CORRECT ORDER

        int element;
        int temp;

        for (int i = 1; i < id.Length; i++)
        {
            element = i - 1;

            while (element >= 0 && id[element] > id[element + 1])
            {
                temp = id[element];
                id[element] = id[element + 1];
                id[element + 1] = temp;
            }
        }

        for (int i = 1; i < id.Length; i++)
        {
            lstPlayers.Items.Add(id[i]);
        }

        txtAddElement.Text = "";
    }

I know this insertion sort works because I have manually added some values in previously, however the basic part now seems to be tripping me up.

What I want is for the program to run with an empty array, as coded above, when I enter a value into txtAddElement I want to use a button btnAddToArray to insert this value into the array. For example:

if i type 12 into txtAddElement, and then press btnAddToArray, i would like the array to now have 1 item of 12, If was was to then add another number via the txtAddElement, lets say 7, and press the btnAddToArray button, I want the array to then have 2 values [12, 7] once I have mastered this then alls i need to do is add the insertion sort to this.

error:

CODE SNIPPET

   int[] id;

    private void btnLogOn_Click(object sender, EventArgs e)
    {
        Array.Resize(ref id, id.Length + 1); //Object reference not set to an instance of an object.
        id[id.Length - 1] = Convert.ToInt16(txtLogOn.Text);

        //INSERTION SORT
        int element;
        int temp;

SOLVED:

  int[] id = new int[0];

Ok if button is clicked then this handler is invoked and sort works but it doesn't take any values from textbox directly. So where is the 'textbox part' of your code ? — Fabjan
– Fabjan, Commented Nov 25, 2015 at 12:31
the question I have been asked says use an array, otherwise I would have no issues with this — dragonAMC
– dragonAMC, Commented Nov 25, 2015 at 12:32
i am using the btnAddToArray to control the text box, once the button is pressed, I want this button to add the item into the array, and then it will empty the textbox — dragonAMC
– dragonAMC, Commented Nov 25, 2015 at 12:33

Dmitrii Bychenko · Accepted Answer · 2015-11-25 12:31:22Z

3

You can't add to array. You should either use List<T> e.g.

  List<int> id;
  ...

  id.Add(123);

Or re-size the array (not recommended)

  int[] id;
  ... 
  Array.Resize(ref id, id.Length + 1);
  id[id.Length - 1] = 123;

answered Nov 25, 2015 at 12:31

Dmitrii Bychenko

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6 Comments

Иво Недев Over a year ago

(In general) Why wouldn't it be recommended to re-size the array ?

Dmitrii Bychenko Over a year ago

@Иво Недев: it could be resource consuming - array (unlike List<T>) is designed as constant size collection.

steavy Over a year ago

Because this logic is already implemented for you in Lists. And it's very likely that you'll make bugs while implementing what is already done.

dragonAMC Over a year ago

each time I run the program the array will be null, so the array size isnt going to be that great, I have to show more that I can do it rather than whats the most efficient was. thankyou for your help, and I shall be using Lists normally from now on!!

dragonAMC Over a year ago

ahh when adding in the resize it states "object reference not set to an instance of an object" see above

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