how to intigrate constant contract API WITH ASP.NET?

There is no such thing as "constant contact". Is this the name of that API?

If you can explain what you want that library or API to do, maybe I can help you out. :-) What function do you need?

Dear Afzaal , Thanks for ur reply.. am looking for api intigration that is constant contact ..api with asp.net .. please help me if possible

Which API do you want to integrated? Usually you just copy/paste (or deploy) the dll files for that API or library.

Then those library functions and features are added to your application automatically. Can you share which library or API you want to use?