CODEWITHSUNDEEP
c#asp.net
Mat
Mat

Reputation: 15

adding a new items to a list. I think either the original items are being overwritten every time or a new list is being created each time

I'm using asp.net 4 and C#. I'm having problems adding items to a list via an event from a button click. On the button click I want to read the text from a text box, convert it to an int and add it to the bottom of a List of type int. I then want to display each item in the List in a label. The problem is that it only displays the most recent textbox entry each time. I've spent ages looking at this and trying different things but cant work out what i'm doing wrong. Please can anybody help?

My code is as follows:

namespace CSI
{
    public partial class _Default : System.Web.UI.Page

{

string lablelItems;

List<int> numbers = new List<int>();

    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void AddToSeqBTN_Click(object sender, EventArgs e)
    {
        int number;
        number = Convert.ToInt32(AddNumberTXB.Text);
        numbers.Add(number);
        printtolabel(numbers);

    }

    private void printtolabel(List<int> numbers)
    {
        foreach (int n in numbers)
        {
            lablelItems += " " + n.ToString();
            CurrentSequenceLBL.Text = lablelItems;
        }
    }

Upvotes: 0

Views: 134

Answers (3)

Justin Harvey
Justin Harvey

Reputation: 14672

In your handler method 

AddToSeqBTN_Click

just do this instead:

CurrentSequenceLBL.Text += " " + Convert.ToInt32(AddNumberTXB.Text);

Upvotes: 1

Tim Schmelter
Tim Schmelter

Reputation: 460158

HTTP is stateless. That means in ASP.NET that all objects are destroyed at the end of the page life-cycle. So as soon as the page is rendered to the client, it won't exist anymore in the server's memory.

So you need to persist the items somewhere.

Nine Options for Managing Persistent User State in Your ASP.NET Application.

Upvotes: 3

Andre Calil
Andre Calil

Reputation: 7692

The list numbers is being re-instantiated for each postback your page receives. You must store it's reference somewhere, like on the Session (at the server) or send it to the ViewState (to the client).

Also, when you say "add it to the bottom", is it literal? I mean, is the position important to you? Because, if it is, you should use another class, like a Queue, because List does not ensure position.

Upvotes: 0

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