DownloadTaskDemo.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading;

namespace DownloadTaskDemo
{
    public class DownloadTaskManager
    {
        private List<DownloadTask> tasks = new List<DownloadTask>();

        public IEnumerable<DownloadTask> Tasks { get { return tasks.AsEnumerable(); } }

        public double Progress { get; private set; }

        public event EventHandler TasksProgressChanged;

        public void Add(DownloadTask task)
        {
            task.ProgressChanged += Task_ProgressChanged;

            tasks.Add(task);
        }

        private void Task_ProgressChanged(object sender, EventArgs e)
        {
            Progress = tasks.Average(x => x.Progress);

            TasksProgressChanged?.Invoke(this, e);
        }

        public void StartAllTasks()
        {
            tasks.ForEach(x => x.Start());
        }
    }

    public class DownloadTask : IDisposable
    {
        private readonly WebClient webClient;
        private bool disposedValue = false;

        public Uri Uri { get; private set; }

        public string FilePath { get; private set; }

        public double Progress { get; private set; }

        public long BytesReceived { get; private set; }

        public long TotalBytesToReceive { get; private set; }

        public event EventHandler ProgressChanged;

        public DownloadTask(Uri uri, string filePath)
        {
            Uri = uri;
            FilePath = filePath;

            webClient = new WebClient();
            webClient.DownloadProgressChanged += WebClient_DownloadProgressChanged;
        }

        private void WebClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            Progress = (double)e.ProgressPercentage / 100;
            BytesReceived = e.BytesReceived;
            TotalBytesToReceive = e.TotalBytesToReceive;

            ProgressChanged?.Invoke(this, e);
        }

        public void Start()
        {
            webClient.DownloadFileAsync(Uri, FilePath);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                if (disposing)
                {
                    webClient.Dispose();
                }

                disposedValue = true;
            }
        }

        public void Dispose()
        {
            Dispose(true);
        }
    }

    //=============================================================================================
    // IMPORTANT: Just for demo purpose, please enhance before using it in production environment.
    //=============================================================================================
    class Program
    {
        static DownloadTaskManager downloadTaskManager = new DownloadTaskManager();
        static Timer timer = new Timer(Timer_Elapsed);

        static void Main(string[] args)
        {
            downloadTaskManager.Add(new DownloadTask(new Uri("http://old-releases.ubuntu.com/releases/18.10/ubuntu-18.10-desktop-amd64.iso"), "ubuntu-18.10-desktop-amd64.iso"));
            downloadTaskManager.Add(new DownloadTask(new Uri("http://old-releases.ubuntu.com/releases/18.10/ubuntu-18.10-live-server-amd64.iso"), "ubuntu-18.10-live-server-amd64.iso"));
            downloadTaskManager.Add(new DownloadTask(new Uri("http://old-releases.ubuntu.com/releases/18.10/ubuntu-18.10-server-ppc64el.iso"), "ubuntu-18.10-server-ppc64el.iso"));
            downloadTaskManager.Add(new DownloadTask(new Uri("http://old-releases.ubuntu.com/releases/18.10/ubuntu-18.10-server-arm64.iso"), "ubuntu-18.10-server-arm64.iso"));
            downloadTaskManager.Add(new DownloadTask(new Uri("http://old-releases.ubuntu.com/releases/18.10/ubuntu-18.10-server-amd64.iso"), "ubuntu-18.10-server-amd64.iso"));

            downloadTaskManager.StartAllTasks();

            timer.Change(0, Timeout.Infinite);

            while (Console.ReadKey().KeyChar != 'q') ;
        }

        static void Timer_Elapsed(object state)
        {
            Console.Clear();

            Console.WriteLine("+----------------------------------------+---------------+");
            Console.WriteLine("| File                                   | Progress (%)  |");
            Console.WriteLine("+----------------------------------------+---------------+");
            foreach (var task in downloadTaskManager.Tasks)
            {
                Console.WriteLine("| {0,-39}| {1,-14}|", task.FilePath, (int)(task.Progress * 100));
            }
            Console.WriteLine("+----------------------------------------+---------------+");
            Console.WriteLine("| All Progress                           | {0,-14}|", (int)(downloadTaskManager.Progress * 100));
            Console.WriteLine("+----------------------------------------+---------------+");

            timer.Change(500, Timeout.Infinite);
        }
    }
}