EDIT: Use the static method Uri.UnescapeDataString() to decode your URLs:
Encoded: http%3a%2f%2fwww.google.com%2fsearch%3fhl%3den%26q%3dsomething%20%2323%26btnG%3dGoogle%2bSearch%26aq%3df%26oq%3d
Decoded: http://www.google.com/search?hl=en&q=something #23&btnG=Google+Search&aq=f&oq=