DotNetOpenAuth is a .NET library that enables OpenID, OAuth and InfoCard support to be easily added to your web and/or desktop applications.
The project site for this library is hosted at http://dotnetopenid.googlecode.com/. Please visit that web site for documentation, support and maintenance releases.
As with any library that is used for security-sensitive purposes such as authentication and authorization, you should periodically check the project web site for updates to this library before and after you install it into a desktop or web application.