Saving asp:Panel state

Question

I'm working on a project in ASP.net (C#) and I have some trouble in concern with the asp:Panel.

Basically, I have an asp:UpdatePanel in which I have a asp:Panel; I Also have asp:TextBox and a button. What I want to do is that : when the user enters text in the asp:TextBox, and then hit the button, the text in the TextBox should Appear in the asp:Panel as a Linkbutton. The Method looks like this :

   protected void AddExchange_Click(object sender, EventArgs e)
    {
        LinkButton link2 = new LinkButton();
        link2.Text = AddAdditionalTxt.Text;
 //   link2.Command += new CommandEventHandler(LinkButton_Command);


        ExchangePanel.Controls.Add(link2);

    }

It works, and it adds the text as a linkButton to the panel, BUT, when i want to add more, the linkButton which has been added before get overwritten. I want to hold some LIST<string> Variable that'll hold all the strings, But whenever the page PostBack it gets deleted.

I would really appreciate if someone could tell me how to solve it - How do i keep a variable (List<>) in a page with UpdatePanel so every PageLoad I can add all the strings in the list inside the asp:Panel.

Thanks in advance.

Answer 1

this code works for me, the ViewState will keep the List<string> the time the user stays in the page

    protected void AddExchange_Click(object sender, EventArgs e)
    {
        List<string> stringList;
        if (ViewState["stringList"] == null)
            stringList = new List<string>();
        else
            stringList = ViewState["stringList"] as List<string>;

        stringList.Add(AddAdditionalTxt.Text);
        foreach (string myStr in stringList)
        {
            LinkButton link2 = new LinkButton();
            link2.Text = myStr;
            //   link2.Command += new     CommandEventHandler(LinkButton_Command);
            ExchangePanel.Controls.Add(link2);
        }
        ViewState["stringList"] = stringList;
    }