Where are tutorials for DotNetOpenAuth and how to solve compile error in its samples

Question

I know stackoverflow uses OpenID authentication. I want to try and use this as well. I am using asp.net mvc 2.0 with C#.

I found this

http://www.dotnetopenauth.net/

and I am wondering if this is what was used for stackoverflow.

Also any tutorials would be nice as well.

Edit

I am trying to load up some sample projects but when I build it in VS2010 I get

Error   6   'System.Diagnostics.Contracts.ContractInvariantMethodAttribute' is inaccessible due to its protection level C:\Users\chobo2\Downloads\DotNetOpenAuth-3.4.6.10357\DotNetOpenAuth-3.4.6.10357\Samples\OpenIdOfflineProvider\TextBoxTextWriter.cs  73  4   OpenIdOfflineProvider
Error   7   The type or namespace name 'ContractInvariantMethod' could not be found (are you missing a using directive or an assembly reference?)   C:\Users\chobo2\Downloads\DotNetOpenAuth-3.4.6.10357\DotNetOpenAuth-3.4.6.10357\Samples\OpenIdOfflineProvider\TextBoxTextWriter.cs  73  4   OpenIdOfflineProvider

Answer 1

Yes, it is the library SO uses. See this blog post from Jeff:

we have an excellent dialog with Andrew Arnott, the primary author of the open source DotNetOpenAuth library we use.

The download includes samples.

Answer 2

I have just found this tutorial which is useful.

Edit: This one also looks worth a read.

And I also found this example useful.