Question

I want to add new items to my generic list when user clicks on a button, but each the the list contains only the last introduced item, it seems that during each button click list get reinitialized :(.

This is a part of code:

 List<ProdusBon> listaProduseBon = new List<ProdusBon>();

protected void Page_Load(object sender, EventArgs e)
{
}

protected void Button1_Click(object sender, EventArgs e)
{
    listaProduseBon.Add(new ProdusBon(-1, Int32.Parse(TextBox2.Text), -1, Int32.Parse (ListBox1.SelectedValue)));
}

I also tried using this code:

 List<ProdusBon> listaProduseBon = null;

protected void Page_Load(object sender, EventArgs e)
{
 if (!Page.IsPostBack)
    {
       listaProduseBon = new List<ProdusBon>();
    }
}

protected void Button1_Click(object sender, EventArgs e)
{
    listaProduseBon.Add(new ProdusBon(-1, Int32.Parse(TextBox2.Text), -1, Int32.Parse (ListBox1.SelectedValue)));
}

but in this case a null reference exception was raised.

I must keep all the items in the list and not only the last one, and when click event was raised a new item to be added to the list.

All the controls in Default.aspx got the default values only the ListBox has “Enable AutoPostBack” set to true but i believe that this is not causing this behavior.

I do not how to keep the items in the list in these conditions, please give me a hand if you know how to do this.

Thanks !

Answer 1

Member variables are lost between page loads. You could store the variable in Session if you want it to remain the same value between loads.

List<ProdusBon> listaProduseBon
{
   get { return (List<ProdusBon>) Session["ProdusBon"]; }
   set { Session["ProdusBon"] = value; }
}

protected void Page_Load(object sender, EventArgs e)
{
    if (listaProduseBon == null) listaProduseBon = new List<ProdusBon>();
}

protected void Button1_Click(object sender, EventArgs e)
{
    listaProduseBon.Add(new ProdusBon(-1, Int32.Parse(TextBox2.Text), -1, Int32.Parse (ListBox1.SelectedValue)));
}