How to use web craling in c#.net?

Question

Hi,

I am creating new application in c# windows application  like google search. I have only one textbox and button, when i type single word(not full URL) in textbox then click button then I need find the list external URL.

 

please guide me. 

 

How can i use web crawler?

Can we create index in local for  External URL?

Please guide me.