Ok so I have a checkbox list with n checkboxes. Everytime I check a box I want that number to get added to a list (Chosen). When the box is unchecked I want to remove it from the list. Then when I hit a button I want to display the list in a textbox. Here is my code:

```
public partial class _Default : System.Web.UI.Page
{
    List<int> Chosen = new List<int>();

    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["Chosen"] == null)
        {
            Session["Chosen"] = new List<int>();
        } 

        Chosen = (List<int>)Session["Chosen"];

        for (int i = 0; i < Numbers.Items.Count; i++)
        {
            if (Numbers.Items[i].Selected) { Chosen.Add(i + 1); }
            else { Chosen.Remove(i + 1); }
        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        foreach (var i in Chosen)
        {
            TextBox1.Text = Chosen[i].ToString();
        }
    }
}

```

Needless to say it does not work the way I want it to. When I select 1 and hit the button it writes 1 into the box, but if I unselect it and hit the button it leaves 1 there. Also if I select any number other than 1 I get an error on this line:

```
TextBox1.Text = Chosen[i].ToString();

```

Saying index is out of range. Yet when I debug the numbers seem to be allocating to the list properly.