title: How to decode OAuth 2.0 for Canvas signed_request in C#?
body: <p>I'm able to successfully validate the signed request for a Facebook canvas app using the example  <a href="https://stackoverflow.com/questions/3385593/c-hmacsha256-problem-matching-facebook-signed-request-implementation">here</a>, but I'm unable to decode the payload.  The Facebook documentation states that the 2nd parameter in signed_request is a base64url encoded JSON object.  In PHP the payload is decoded using json_decode:</p>
  
  <pre><code>$data = json_decode(base64_url_decode($payload), true);
  </code></pre>
  
  <p>What is the equivalent in C#? </p>