Can any one suggest me to best C# twitter api for developing application with twitter api?. I want all the advance functionality of twitter in my application.
LINQ to Twitter, if your app is LINQ-enabled.
"LINQ to Twitter is a LINQ Provider for the Twitter micro-blogging service. It uses standard LINQ syntax for queries and includes method calls for changes via the Twitter API."
I haven't used this myself, just found it when browsing and passing it on. It's interesting that if you search with the #linqtotwitter hashtag, you can see all the test tweets, which all start with "Ç".
May I humbly suggest TweetSharp. It has full support for the API including the Search API and updates are released as soon as possible to address changes in the twitter API. (for instance, it already supports the upcoming GeoLocation APIs).
It's open source (MIT license), so you can use it free for pretty much anything you want.
Disclosure: I'm a project owner.