c# - Selecting an item in a GridView and adding to the List -

i have written piece of code below productid gridview when user clicks on select link.

convert.toint32(gridview1.selecteddatakey.values["productid"])))

however, if user clicks on more 1 click newer value replaces previous. there way keep adding cart list when user clicks on new item?

hope makes sense

thanks

edit:

here's code shopping page:

public partial class _default : system.web.ui.page {     list<basketclass> cart = new list<basketclass>();      protected void gridview1_selectedindexchanged1(object sender, eventargs e)     {         cart.add(new basketclass(convert.toint32(gridview1.selecteddatakey.values["bookid"])));          session.add("cartsess", cart);         response.redirect("basket.aspx");     } } 

i dont know if location of creating list important? wasn't sure if placed in click event if keep creating new instance?

then basket page have:

protected void page_init(object sender, eventargs e) {     list<basketclass> cart = (list<basketclass>)session["cartsess"];      foreach (basketclass bookid in cart)     {              gridview1.datasource = cart;         gridview1.databind();         accessdatasource1.selectcommand = "select [bookid], [book_title] [tblbook] ";                          } } 

you should not create basketcart list object in top of page, if there no significant difference, think cna this:

protected void page_init(object sender, eventargs e) {         if(session["cartsess"]!=null)     {            foreach (basketclass bookid in (list<basketclass>)session["cartsess"])        {               gridview1.datasource = cart;          gridview1.databind();         accessdatasource1.selectcommand = "select [bookid], [book_title] [tblbook] ";                             }     } } 

and gridview should be:

protected void gridview1_selectedindexchanged1(object sender, eventargs e) {    list<basketclass> cart;    if(session["cartsess"]!=null)    {         cart = (list<basketclass>)session["cartsess"]    }    else      cart = new list<basketclass>();     cart.add(new basketclass(convert.toint32(gridview1.selecteddatakey.values["bookid"])));     session.add("cartsess", cart);    response.redirect("basket.aspx"); }