HttpWebRequest，如何使用应用程序/ JSON内容类型发送POST数据？

byte[] data = CreateData(value);
var requst = (HttpWebRequest) WebRequest.Create(uri);
requst.Method = \"POST\";
requst.ContentType = \"application/json\";
requst.ContentLength = data.Length;
using (Stream stream = requst.GetRequestStream())
{
    stream.Write(data, 0, data.Length);
}

CreateData

public static byte[] Create<T>(T value)
{
    var serializer = new DataContractJsonSerializer(typeof (T));
    using (var stream = new MemoryStream())
    {
        serializer.WriteObject(stream, value);
        return stream.ToArray();
    }
}

    $.ajax({
        type: \'POST\',
        url: \'http://developer.messenger.yahooapis.com/v1/session\',
        data: JSON.stringify({ }),
        processData: false,
        beforeSend: function(xhr) {
            xhr.setRequestHeader(\'Authorization\', OAuth.getAuthorizationHeader(\"yahooapis.com\", message.parameters));
            xhr.setRequestHeader(\'Content-Type\',\'application/json; charset=UTF-8\');
            xhr.setRequestHeader(\'X-Yahoo-Msgr-User-Agent\',\'YahooMessenger/1.0 (yourapp; 1.0.0.1)\')
        }});

httpWebRequest.ContentType = @\"application/json; charset=utf-8\";        
WebHeaderCollection headers = new WebHeaderCollection();
headers.Add(\"Authorization\", \"Bearer \"+oAuthBearerToken);
httpWebRequest.Headers = headers;

ClassLogon objLogon = new ClassLogon
  {
    presenceState = ***0***,
    presenceMessage = \"I am logn\"
  };