I am looking for C # code that can be used to translate Hindi text into English transliteration.
Also tell me if there are api for C #.
From what I see, this is not an easy task, but it can be done. Google provided an API to help: http://www.techdreams.org/google/trick-to-use-google-indic-transliteration-service-in-c-java-php-and-other-programming-languages/1134 -20090122
I know this is a broad answer, but it matches the breadth of the question. You will need to do research on how to implement this in your code.
.NET codeplex: http://unidecode.codeplex.com/ - .
Windows 7+ can do this for Hindi / Devanagari with Advanced Linguistic Services . (You will need the Windows API Code Code to do this from .NET.)