//private InvoiceDL _invoiceDL = new InvoiceDL();
/// <summary>
/// Lấy danh sách hóa đơn
/// </summary>
/// <returns></returns>
public List <Invoice> GetInvoices()
{
InvoiceDL invoiceDL = new InvoiceDL();
List <Invoice> invocies = invoiceDL.GetInvoices();
return(invocies);
}