C#(asp.net) ASHX 파일 읽기(일반 프로세서)

    public string GetResponseByPost(string apiUrl, string queryString)
    {
        string responseString = string.Empty;
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(apiUrl + queryString);
        request.ContentType = "text/html";
        request.Method = "POST";
        request.ContentLength = queryString.Length;
        request.Timeout = 20000;
        byte[] bytes = Encoding.UTF8.GetBytes(queryString);
        Stream os = null;
        try
        { // send the Post
            request.ContentLength = bytes.Length;   //Count bytes to send
            os = request.GetRequestStream();
            os.Write(bytes, 0, bytes.Length);         //Send it
        }
        catch (WebException ex)
        {
            throw ex;
        }
        finally
        {
            if (os != null)
            {
                os.Close();
            }
        }

        HttpWebResponse response = null;
        try
        {
            response = (HttpWebResponse)request.GetResponse();
            using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
            {
                responseString = reader.ReadToEnd();
            }
        }
        catch (Exception ex2)
        {
            throw ex2;
        }
        finally
        {
            if (response != null)
                response.Close();
        }
        return responseString;
    }