deserialize.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Net;
using System.Net.Http;
using Newtonsoft.Json;



namespace ConsoleApp
{

    public class GistObject
    {
        public string url { get; set; }
        public string forks_url { get; set; }
        public string commits_url { get; set; }
        public string id { get; set; }
        public string node_id { get; set; }
        public string git_pull_url { get; set; }
        public string git_push_url { get; set; }
        public string html_url { get; set; }
        public FileObject _files { get; set; }
        public bool _public { get; set; }
        public DateTime created_at { get; set; }
        public DateTime updated_at { get; set; }
        public string description { get; set; }
        public int comments { get; set; }
        public object user { get; set; }
        public string comments_url { get; set; }
        public Owner owner { get; set; }
        public object[] forks { get; set; }
        public History[] history { get; set; }
        public bool truncated { get; set; }
    }

    public class FileObject
    {
        public FileType _file { get; set; }
    }

    public class FileType
    {
        public string _filename { get; set; }
        public string type { get; set; }
        public string language { get; set; }
        public string raw_url { get; set; }
        public int size { get; set; }
        public bool truncated { get; set; }
        public string content { get; set; }
    }

    public class Owner
    {
        public string login { get; set; }
        public int id { get; set; }
        public string node_id { get; set; }
        public string avatar_url { get; set; }
        public string gravatar_id { get; set; }
        public string url { get; set; }
        public string html_url { get; set; }
        public string followers_url { get; set; }
        public string following_url { get; set; }
        public string gists_url { get; set; }
        public string starred_url { get; set; }
        public string subscriptions_url { get; set; }
        public string organizations_url { get; set; }
        public string repos_url { get; set; }
        public string events_url { get; set; }
        public string received_events_url { get; set; }
        public string type { get; set; }
        public bool site_admin { get; set; }
    }

    public class History
    {
        public User user { get; set; }
        public string version { get; set; }
        public DateTime committed_at { get; set; }
        public Change_Status change_status { get; set; }
        public string url { get; set; }
    }

    public class User
    {
        public string login { get; set; }
        public int id { get; set; }
        public string node_id { get; set; }
        public string avatar_url { get; set; }
        public string gravatar_id { get; set; }
        public string url { get; set; }
        public string html_url { get; set; }
        public string followers_url { get; set; }
        public string following_url { get; set; }
        public string gists_url { get; set; }
        public string starred_url { get; set; }
        public string subscriptions_url { get; set; }
        public string organizations_url { get; set; }
        public string repos_url { get; set; }
        public string events_url { get; set; }
        public string received_events_url { get; set; }
        public string type { get; set; }
        public bool site_admin { get; set; }
    }

    public class Change_Status
    {
        public int total { get; set; }
        public int additions { get; set; }
        public int deletions { get; set; }
    }

    class Program
    {
        static string gistAPIUrl = "http://api.github.com/gists/:gist_id";
        static string url = "https://gist.github.com/PontiacGTX/d99835d35fb2f29e4382bd23656b860f";

        private static int GetIndex(string str, char c, int n)
        {
            int stringPosition = -1;

            for (int i = 0; i < n; i++)
            {
                stringPosition = str.IndexOf(c, stringPosition + 1);

                if (stringPosition == -1) break;
            }
            return stringPosition;
        }
        
        private static void GetGistUrl(ref string localurl, ref string fileName, ref string extension)
        {
            fileName = "";
            string gistAPI = gistAPIUrl;
            int gistIndexBegin = GetIndex(url, '/', 4);
            int gistIndexEnd = url.IndexOf('#', 1) > 0 ? url.IndexOf('#', 1) : url.Length;
            string gistID = url.Substring(gistIndexBegin + 1, gistIndexEnd - (gistIndexBegin + 1));

            gistAPI = gistAPIUrl.Replace(":gist_id", gistID);
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(gistAPI);
            request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36";
            request.Method = WebRequestMethods.Http.Get;
            request.Timeout = 5000;
            Stream response = request.GetResponse().GetResponseStream();
            StreamReader readstream = new StreamReader(response);
            string responsetr = readstream.ReadToEnd();
            readstream.Dispose();
            readstream.Close();
            var gistResultObj = JsonConvert.DeserializeObject<IList<GistObject>>(responsetr).ToList();


            for (int i = 0; i < gistResultObj.Count; i++)
            {
                foreach (FileObject obj in gistResultObj[i]._files)
                {
                    if (!string.IsNullOrEmpty(obj._file.raw_url))
                    {
                        localurl = obj._file.raw_url;
                    }
                    if (!string.IsNullOrEmpty(obj._file._filename))
                    {
                        fileName = obj._file._filename;
                    }
                }
            }

            if (fileName == "")
            {
                fileName = gistID;
            }

            extension = Path.GetExtension(localurl);
        }
        static void Main(string[] args)
        {
            string dlurl, filename, ext;
            dlurl = ""; filename = ""; ext = "";
            GetGistUrl(ref dlurl, ref filename, ref ext);

            Console.ReadKey();
        }
    }
}