Http client Downloader for Retry(Palmer lib)/Resume download requests enabled.

gistfile1.txt

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Security;
using System.Reflection;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Palmer;

namespace ConsoleApplication1
{
    internal class Program
    {
        public static void Main(string[] args)
        {
            Console.WriteLine("Starting download.... ");
            try
            {
                DownloadFile("https://github.com/MitchDenny/Palmer/archive/master.zip", "C:\\Temp\\packages.zip");
            }
            catch (Exception ex)
            {
                if (!string.Equals(ex.Message, "Stack Empty.", StringComparison.InvariantCultureIgnoreCase))
                {
                    Console.WriteLine("========= Error ==========");
                    Console.WriteLine("{0}{1}{1} Inner Exception: {1} {2}", ex.Message, Environment.NewLine,
                                      ex.InnerException.ToString());
                }
            }

            Console.WriteLine("Press enter key to exit.. ");
            Console.Read();
        }


        public static bool DownloadFile(string url, string filepath)
        {
            WebClient client = new WebClient();
            ServicePointManager.ServerCertificateValidationCallback += (sender, certificate, chain, errors) =>
                { return true; };

            // Add a user agent header in case the 
            // requested URI contains a query.
            int count = 1;
            bool result = true;
            Retry.On<Exception>().For(3).With(context =>
                {
                    try
                    {
                        client.Headers.Add("user-agent",
                                           "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

                        client.OpenRead(url);

                        FileInfo finfo = null;

                        if (File.Exists(filepath))
                        {
                            finfo = new FileInfo(filepath);

                            if (client.ResponseHeaders != null &&
                                finfo.Length >= Convert.ToInt64(client.ResponseHeaders["Content-Length"]))
                            {
                                File.Delete(filepath);
                            }
                        }

                        DownloadFileWithResume(url, filepath);

                        
                        // Refresh the file content size
                        finfo = finfo ?? new FileInfo(destinationFilePath);

                        if (finfo.Length == Convert.ToInt64(client.ResponseHeaders["Content-Length"]))
                        {
                            result = true;
                            Console.WriteLine("Download success!!!");
                        }
                        else
                        {
                            result = false;
                            throw new WebException("Download interrupted. Retrying download.. ");
                        }
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine("Error: {0} {1}", ex.Message, Environment.NewLine);
                        Console.WriteLine("Download inturrpted retry({0}).. in 5 seconds", count++);
                        System.Threading.Thread.Sleep(5000);
                        throw;
                    }
                });

            return false;
        }

        private static void DownloadFileWithResume(string sourceUrl, string destinationPath)
        {
            long existLen = 0;
            System.IO.FileStream saveFileStream;
            if (System.IO.File.Exists(destinationPath))
            {
                System.IO.FileInfo fINfo =
                    new System.IO.FileInfo(destinationPath);
                existLen = fINfo.Length;
            }
            if (existLen > 0)
                saveFileStream = new System.IO.FileStream(destinationPath,
                                                          System.IO.FileMode.Append, System.IO.FileAccess.Write,
                                                          System.IO.FileShare.ReadWrite);
            else
                saveFileStream = new System.IO.FileStream(destinationPath,
                                                          System.IO.FileMode.Create, System.IO.FileAccess.Write,
                                                          System.IO.FileShare.ReadWrite);

            System.Net.HttpWebRequest httpWebRequest;
            System.Net.HttpWebResponse httpWebResponse;
            httpWebRequest = (System.Net.HttpWebRequest) System.Net.HttpWebRequest.Create(sourceUrl);
            httpWebRequest.AddRange((int) existLen);
            System.IO.Stream smRespStream;
            httpWebResponse = (System.Net.HttpWebResponse) httpWebRequest.GetResponse();
            smRespStream = httpWebResponse.GetResponseStream();
            var abc = httpWebRequest.Timeout;

            smRespStream.CopyTo(saveFileStream);
            saveFileStream.Close();
        }
    }
}