How to post or get data from or to a outer web api server in asp.net core razor page project

I build a asp.net core razor page website  www.mywebsite.com/wx. There is a api server https://api.outerserver.com/server .When the outer api server post a xml data to mywebsite
www.mywebsite.com/wx  ,My project‘s  task is todo two thing ,the  first task is  get a  token from thehttps://api.outerserver.com/server/gettoken ,the Second task my project read theXml data ,and reply the same xml data to the  outer api server.

Above can be done in mvc project or asp.net webform project.

How to do it in asp.net core razor page project. please show me a sample.

 public static string GetAccessToken(string corpid, string corpsecret)
        {
            string getAccessTokenUrl = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={0}&secret={1}";
            string accessToken = "";        string respText = "";       
            string url = string.Format(getAccessTokenUrl, corpid, corpsecret);

          HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();            using (Stream resStream = response.GetResponseStream())
            {
                StreamReader reader = new StreamReader(resStream, Encoding.Default);
                respText = reader.ReadToEnd();
                resStream.Close();
            }

         try
            {
                int start = respText.IndexOf("access_token");
                int end = respText.IndexOf("expires_in");
                start += 15;
                end -= 3;
                respText = respText.Substring(start, end - start);
                accessToken = respText;
            }
            catch (Exception ex) { }；      return accessToken;
        }