solving equation by c# codes

Google is your friend: Be nice and visit him often. He can answer questions a lot more quickly than posting them here...

A very quick search gave 3.4 million results: Google[^]

In future, please try to do at least basic research yourself, and not waste your time or ours.

Please see this Code Project article
math / function / boolean /string expression evaluator[^]
It may be helpful

Please go through this post,
How to ask a good question?[^]

Seems like Richard tried to crack a joke.
But perhaps he has hit the bulls eye.................

Why dont you implement a webrequest in your form and try hitting the google's url with the written equation passed as parameter to q of the google's get request ;)

http://www.google.co.in/search?q=25%2B85&sourceid=opera&ie=utf-8&oe=utf-8&channel=suggest


And parse the output to the answer box..............
which for me came in following table

25 + 85 = 110 More about calculator.