facebook: Is there a documented way to send facebook updates from an external application?

Is there an official way for sending facebook updates (i.e. wall texts with links) from a (desktop) application?

Does anyone know an existing .NET library for doing this?

There's are several Open Source FB client for .NET:

• The Facebook API for .NET should be able to post updates and more.
• The Facebook Developer Toolkit for .NET has some good tutorials like this one.

Sadly, I have not used these or any of the other .NET clients, so I can't say which is better. In any case, you should get your start at the Facebook Developer's page.