C# - Getting Total For A Column In ListView?

I need to get a sum for all items in a column within a listview. I put in the following code in the itemdatabound event, but realized after testing it that it will only be getting what is bound, oops.

converting this to show a total for my column from all items bound to the ListView.

if (e.Item.ItemType == ListViewItemType.DataItem)
{
ListViewDataItem item = (ListViewDataItem)e.Item;
Label lblQty = (Label)e.Item.FindControl("lblQuantity");
if (lblQty == null)
{
return;
}
if (lblQty.Text.Length == 0 || lblQty.Text == "")
{
return;
}
else
{
ListViewTotal += int.Parse(lblQty.Text);
}
}