protected void companyDropDownList_SelectedIndexChanged(object sender, EventArgs e)
        {
            int companyId = Convert.ToInt32(companyDropDownList.SelectedItem.Value);

            itemDropDownList.DataSource     = aStockInManager.GetAllItemByCompanyId(companyId);
            itemDropDownList.DataValueField = "ItemId";
            itemDropDownList.DataTextField  = "ItemName";
            itemDropDownList.DataBind();
            itemDropDownList.Items.Insert(0, new ListItem("Select", "0"));
        }