I recently updated documentation for v3.0, where I renamed some items to better reflect their purpose and add more consistency to the library. Here's how that should look in 2.1.11:
var auth = new MvcAuthorizer
{
CredentialStore = new SessionStateCredentials
{
ConsumerKey = ConfigurationManager.AppSettings["consumerKey"],
ConsumerSecret = ConfigurationManager.AppSettings["consumerSecret"]
}
};
The downloadable source code has a project named LinqToTwitterMvcDemo with an example: