调用GetResponse()抛出(500)内部服务器错误

是什么导致这个异常被抛出，以及如何补救

我正在向服务器发送API Post，传递一个序列化的XML文件，并且我期望一个返回调用。

相反，我的代码在GetResponse()调用时抛出500内部服务器错误。

我已经检查了我文件的语法，它是正确的。我也知道我的逻辑工作，因为我已经在其他调用中使用了它。

try
    {                       
        wWebRequest = (HttpWebRequest)WebRequest.Create(strWebAddressAuthentication);
        wWebRequest.CookieContainer = new CookieContainer();
        wWebRequest.Method = sHTTPTransMethod;
        wWebRequest.ServicePoint.Expect100Continue = false;
        wWebRequest.UserAgent = sUserAgent;
        wWebRequest.ContentType = srequestContentType;
        FileInfo fInfo = new FileInfo(filename);
        long numBytes = fInfo.Length;
        double dLen = Convert.ToDouble(fInfo.Length / 1000000);
        if (dLen < 100)
        {
            fStream = new FileStream(filename, FileMode.Open, FileAccess.Read);
            br = new BinaryReader(fStream);
            data = br.ReadBytes((int)numBytes);
            br.Close();
            wWebRequest.ContentLength = data.Length;                    
            dataStream = wWebRequest.GetRequestStream();
            dataStream.Write(data, 0, data.Length);
            dataStream.Close();
            response = (HttpWebResponse)wWebRequest.GetResponse();
            foreach (Cookie cook in response.Cookies)
            {
                myCookieContainer.Add(cook);
            }
            txtXmlReturned.Text = (((HttpWebResponse)response).StatusDescription);
            sServerResponse = txtXmlReturned.Text + Environment.NewLine;
            dataStream = response.GetResponseStream();
            reader = new StreamReader(dataStream);
            responseFromServer = reader.ReadToEnd();
            txtXmlReturned.Text = txtXmlReturned.Text + responseFromServer + Environment.NewLine;
            reader.Close();
            response.Close();
            fStream.Close();
            fStream.Dispose();
            // -----------------------------------------------------------
        }
        else
        {
            MessageBox.Show("The file selected exceeds the size limit for uploads.", "File Size");
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message.ToString(), "Upload Error");
    }
}