WhoisClient.dll is a .NET component for domain names whois search.You can integrate Whois searches with your application using any .NET language. WhoisClient.dll was written entirely in managed code. It can perform recursive whois queries and automatically finds the correct whois server. It is possible to override a given whois server and use a custom whois server for better performance.
When a WHOIS query is conducted it speaks with a WHOIS server and asks it to return all the information it has available about a particular domain. The Domain records are then returned so you can see the Administrative, technical, Zone and other contacts. You also find out the DNS servers used for the website and contact information about the owner. Such as the name, address, phone number and sometimes email address of the registrant.
You can add quick domain name checking capabilities to your program, allowing your users to see the owners of domain names and also see if they are not currently registered. There are many applications for this component.