protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                purchaseOrderControl = GetControl();
                StationeryStoreInventorySystemController.Util.PutSession(sessionKey, purchaseOrderControl);

                //FillItemsGridView();

                //FillItems();
                FillSupplier();
                FillItems();
                lblPONumber.Text = purchaseOrderControl.PurchaseOrderId.ToString();
                //FillDataGrid();
            }
            else
            {
                purchaseOrderControl = (PurchaseOrderControl)StationeryStoreInventorySystemController.Util.GetSession(sessionKey);
            }
            //FillItemsGridView();
        }
 private PurchaseOrderControl GetControl()
 {
     if (purchaseOrderControl == null)
         purchaseOrderControl = new PurchaseOrderControl();
     return purchaseOrderControl;
 }