Application generated apprequests failing in Silverlight

Question

I'm trying to send an application-generated request between two users without going through the JavaScript UI.

FacebookClient client = new FacebookClient(SessionSecret);

Dictionary<string, string> parameters = new Dictionary<string, string>();
parameters["message"] = "Test";
parameters["data"] = "test";

client.PostCompleted += new EventHandler<FacebookApiEventArgs>(testCompleted);
client.PostAsync(String.Format("{0}/apprequests", ID), parameters);

My testCompleted method FacebookApiEventArgs error is always a null object reference on a stream object that it is expecting:

at System.IO.StreamReader..ctor(Stream stream, Encoding encoding, Boolean
detectEncodingFromByteOrderMarks, Int32 bufferSize)
at System.IO.StreamReader..ctor(Stream stream)
at Facebook.FacebookClient.ProcessResponse(HttpHelper httpHelper, Stream
responseStream, Type resultType, String& responseStr, Exception& exception, Boolean&
cancelled)

This is on 5.2.1.

Am I doing it wrong? I've also tried instantiating the client using the App ID and secret with the same results.

It looks like a bug in the Facebook client code in the PrepareRequest method at line 1671:

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");
    }

It's only putting in the parameters passed to the method for Get calls, not for post.

Answer 1

I went down a rabbit hole, but I didn't need to. In fact, the problem lies in the fact that I was using the users accessToken instead of generating a new accessToken from the application id and applications secret. The first line should instead be:

FacebookClient client = new FacebookClient(AppId, AppSecret);