title: Where are tutorials for DotNetOpenAuth and how to solve compile error in its samples
body: <p>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#.</p>
  
  <p>I found this</p>
  
  <p><a href="http://www.dotnetopenauth.net/" rel="noreferrer">http://www.dotnetopenauth.net/</a></p>
  
  <p>and I am wondering if this is what was used for stackoverflow. </p>
  
  <p>Also any tutorials would be nice as well.</p>
  
  <p>Edit</p>
  
  <p>I am trying to load up some sample projects but when I build it in VS2010 I get</p>
  
  <pre><code>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
  </code></pre>