Hi Pure.Krome. Have we exchanged messages on StackOverflow?
So first let's talk about your original problem. Twitter doesn't accept 'localhost'? In my test yesterday this worked fine. Twitter doesn't accept 'localhost' in the callback that you register with them at twitter.com/oauth_clients, but
it does seem to accept it and behave correctly if you pass localhost from your actual web app, and it works fine from my dev box. Have you tried putting a regular URL into /oauth_clients and then allowing localhost to go in from linq2twitter?
If that doesn't work, we should explore why, since it works for me. But I'm also curious what you would put instead of localhost, since anything else wouldn't complete the OAuth flow and you wouldn't regain control after sending the user to Twitter.
Finally, if you really want to customize the callback parameter, you'd have to modify the LinqToTwitter.WebOAuthAuthorization class's BeginAuthorization method to call the overload that takes a customized callback parameter.
public void BeginAuthorize()
this.Consumer.Channel.Send(this.Consumer.PrepareRequestUserAuthorization(new Uri("someUri"), null, null));