static void Main(string[] args)
{
PrePaidInvoice p = new PrePaidInvoice();
p.GetDate();
p.DoPrint();
Console.ReadKey();
}
private static void UsingBaseExample()
{
PrePaidInvoice p = new PrePaidInvoice();
p.GetDate();
/* When the DoPrint method is called on an instance of the PrePaidInvoice class, it first
* makes a call of the DoPrint method in the parent object. */
p.DoPrint();
}