title: Real-Time Subscriptions
body: <p>Good afternoon,
  I'm using version 5.4.1 of the Facebook C# SDK. I should note that I am using the source code directly rather than the DLLs (in case this makes any difference).</p>
  
  <p>So the fact that filter attributes are setup is awesome (thank you dev team :).</p>
  
  <p>My issue is occurring during the initial request (before I get to using verifying the GET response from Facebook)</p>
  
  <p>Here is my initial request:         </p>
  
  <pre><code>dynamic result = fb.Post(
                  string.Format("/{0}/subscriptions", 
                       FacebookApplication.Current.AppId),
                  new Dictionary&lt;string, object&gt;
                      {
                          {"object", "user"},
                          {"fields", "friends"},
                          {
                              "callback_url",
                              "http://localhost:16917/subscription/verify"
                              },
                          {
                              "verify_token",
                              "77FB802F-1147-48F0-BB0F-E4E9BC1FBCFC"
                              }
                      });
  </code></pre>
  
  <p>I'm finding that an exception is internally being thrown and via Fiddler I'm seeing that the request is never going out. The exception is: </p>
  
  <pre><code>$exception  {"(OAuthException) (#15) This method must be called with an app access_token."} System.Exception {Facebook.FacebookOAuthException}
  </code></pre>
  
  <p>I initially thought this may be related to Facebook.FacebookClient's PrepareRequest method:</p>
  
  <pre><code>if (httpMethod == HttpMethod.Get)
  {
      // for GET, all parameters goes as querystrings
      input = null;
      queryString.Append(FacebookUtils.ToJsonQueryString(parameters));
  }
  else
  {
      if (parameters.ContainsKey("access_token"))
      {
          queryString.AppendFormat("access_token={0}", parameters["access_token"]);
          parameters.Remove("access_token");
      }
  }
  </code></pre>
  
  <p>but commenting out the line <code>parameters.Remove("access_token");</code> made no difference.</p>
  
  <p>Any help would be greatly appreciated!</p>