protected void btnAllStock_Click(object sender, EventArgs e)
{
//create an instance of clsStockCollection
clsStockCollection Stock = new clsStockCollection();
Stock.ClearFilter();
lstStock.DataSource = Stock.StockList;
//set name of primary key
lstStock.DataValueField = "ItemId";
//set name of field to display
lstStock.DataTextField = "ItemName";
//bind data to the list
lstStock.DataBind();
}