c# - 在读取异常时执行 webrequest 和接收错误：底层连接已关闭：接收时发生意外错误

Question

我正在尝试在 asp.net4.0 c# 中进行发布请求。但我在阅读响应时收到错误。

错误：异常：基础连接已关闭：接收时发生意外错误。

  public static string PostWithResponse(string PostUrl, string DataUrl, string PostContentType, bool isTimeOut, int ResponseTimeOut)            
  {
        string returnPostResponse = string.Empty;
        HttpWebRequest PostRequest = (HttpWebRequest)WebRequest.Create(PostUrl);
        PostRequest.ContentType = PostContentType;
        PostRequest.Method = "POST";
        byte[] bytes = Encoding.ASCII.GetBytes(DataUrl);
        Stream os = null;
        try
        {
            PostRequest.ContentLength = bytes.Length;
            os = PostRequest.GetRequestStream();
            os.Write(bytes, 0, bytes.Length);
            if (isTimeOut)
            {
                PostRequest.Timeout = ResponseTimeOut;
            }
        }
        catch (Exception ex)
        {
            //
        }
        finally
        {
            if (os != null)
            {
                os.Close();
            }
        }

        try
        {
            HttpWebResponse PostResponse = (HttpWebResponse)PostRequest.GetResponse();
            if (PostResponse == null)
            {
                //
            }
            StreamReader sr = new StreamReader(PostResponse.GetResponseStream());
            returnPostResponse = sr.ReadToEnd().Trim();
        }
        catch (Exception ex)
        {
            //Error Found Here
        }
        return returnPostResponse;
  }