The complete self devloped who is lookup using ASP.net and C# is available for download at 

 http://satalajwhois.codeplex.com/

It uses Socket programming and connects to port 43. It almost query all domain types for who is lookup.
e.g. .in , .com, .au, .pk, .en, .uk, .us, .cn,
It has facility to add new domain type and its registarar.