底层连接已关闭：接收asmx发生意外错误

Question

我有一个xml文件，其中包含iefile.xml

<soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
  <soap12:Body>
    <authorise  xmlns="http://tempuri.org/">
      <value1>{0}</value1>
      <value2>{1}</value2>
    </authorise>
  </soap12:Body>
</soap12:Envelope>

我有一个asmx网络服务，我称之为：

string[] data = { "Value1", "Value2"};

using (WebClient client = new WebClient())
{
    client.Proxy = null;
    client.Headers.Add(HttpRequestHeader.ContentType, "application/soap+xml; charset=utf-8");
    client.Headers.Add("SOAPAction", "http://tempuri.org");
    StreamReader reader = new StreamReader(path); //path to xml file i.e file.xml

    MyData = String.Format(reader.ReadToEnd(), data);
    reader.Close();
    ServicePointManager.Expect100Continue = true;
    ServicePointManager.ServerCertificateValidationCallback +=
       delegate(
           object sender1,
           X509Certificate certificate,
           X509Chain chain,
           SslPolicyErrors sslPolicyErrors)
       {
           return true;
       };

    rst = client.UploadString(new Uri(https://myasmxwebservice.asmx), MyData); //Throws exception from here
}

它一直工作正常，直到我开始出错 “基础连接已关闭：接收时发生意外错误。”我不知道这个问题，也不知道如何解决它。