follows these steps for that type of shopping cart with wishlist.
step 1; first u add more item in your wishlist as u done.
step2: select some item from wishhllist by selecting checkbox in gridview.
Step3: on click event of checkout button u put this code for getting all checked row id
/// method to retrieve all the selected items in the GridView
/// NOTE: This is so we dont lose track of them while paging
private void GetCheckedItems(string crtl,GridView grdView)
//instantiate new ArrayList to hold our checked items
ArrayList checkedItems = new ArrayList();
string chkBoxIndex = string.Empty;
//loop through each row in the GridView
foreach (GridViewRow row in grdView.Rows)
//get the index of the current CheckBox
chkBoxIndex = (string)grdView.DataKeys[row.RowIndex].Value.ToString();
chk = (CheckBox)row.FindControl(ctrl);
//add ArrayList to Session is if doesnt already exist
if (!(Session["CheckedItems"] == null))
checkedItems = (ArrayList)Session["CheckedItems"];
//now see if the current CheckBox is checked
//see if the current value is in the Session, if not add it
//add to the list
//remove from list since it's unchecked
//update Session with the list of checked items
Session["CheckedItems"] = checkedItems;
Step4: after the u can populate that selected id on the shopping cart page from database.