HttpWebResponse with multiple URL causes error

问题

I have this code:

public class WebDataDownloader
{
    public string GetJSONFromURL(string url)
    {
         string file = string.empty;
         //*********get the json file using httpRequest ***********

         try
         {
            HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
            httpWebRequest.Method = WebRequestMethods.Http.Get;
            httpWebRequest.Accept = "application/json; charset=utf-8";
            //httpWebRequest.UserAgent = @"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36";
            //ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;

            using (var response = (HttpWebResponse)httpWebRequest.GetResponse())
            {
                using (var sr = new StreamReader(response.GetResponseStream()))
                {
                    file = sr.ReadToEnd();
                }
            }
        }
        catch(Exception exp)
        {
            Debug.WriteLine(exp.Message);
        }

        return file;
    }
}

Now I call this method from multiple times to get JSON and parse it. Something as given below:

public class MyClass
{
    WebDataDownloader myWebClient = new WebDataDownloader();
    string Json1 = myWebClient.GetJSONFromURL(@"https://www.nseindia.com/api/market-data-pre-open?key=ALL");

    //Do some action on this data

    string Json2 = myWebClient.GetJSONFromURL(@"https://www.nseindia.com/api/equity-stock?index=fu_nifty50");

    //Do some action on this data

    string Json3 = myWebClient.GetJSONFromURL(@"https://www.nseindia.com/api/liveEquity-derivatives?index=nifty_bank_fut");

    //Do some action on this data
}

But, the problem is, the first call for (Json1) using

response = (HttpWebResponse)httpWebRequest.GetResponse()

works fine, but 2nd and 3rd calls does not work in the same instance.

Can anybody please help me with this...

Thanks in advance.

来源：https://stackoverflow.com/questions/61440657/httpwebresponse-with-multiple-url-causes-error