同时处理多个实例化的设计解决方案

我不知道我的标题是否正确。但这就是我想知道的。

我有一个Download类，它返回某些事件并有几个方法。Download类的每个实例都可以下载一个文件。所有这些事件和方法都与正在下载的文件有关。

由于它是一个多文件下载器，当需要下载多个文件时需要多个实例化。

每个下载都有一个下载id，但没有提供给download类，以使其独立于其他类。

现在的问题是从文件下载的每个实例中获取所有信息并能够控制单个下载。我怎么知道哪个下载是哪个?

解决方案吗?或者你可以推荐的设计模式?我遇到了一个障碍。

下载类:

using System;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Threading;
namespace Mackerel_Download_Manager
{
    public class Download
    {
        public event EventHandler<DownloadStatusChangedEventArgs> ResumablityChanged;
        public event EventHandler<DownloadProgressChangedEventArgs> ProgressChanged;
        public event EventHandler Completed;
        public bool stop = true; // by default stop is true
        public bool paused = false;
        SemaphoreSlim pauseLock = new SemaphoreSlim(1);
        string filename;
        public void DownloadFile(Uri DownloadLink, string Path)
        {
            filename = System.IO.Path.GetFileName(Path);
            stop = false; // always set this bool to false, everytime this method is called
            var fileInfo = new FileInfo(Path);
            long existingLength = 0;
            if (fileInfo.Exists)
                existingLength = fileInfo.Length;
            var request = (HttpWebRequest)HttpWebRequest.Create(DownloadLink);
            request.Proxy = null;
            request.AddRange(existingLength);
            try
            {
                using (var response = (HttpWebResponse)request.GetResponse())
                {
                    long fileSize = existingLength + response.ContentLength; //response.ContentLength gives me the size that is remaining to be downloaded
                    bool downloadResumable; // need it for not sending any progress
                    if ((int)response.StatusCode == 206) //same as: response.StatusCode == HttpStatusCode.PartialContent
                    {
                        //Console.WriteLine("Resumable");
                        downloadResumable = true;
                    }
                    else // sometimes a server that supports partial content will lose its ability to send partial content(weird behavior) and thus the download will lose its resumability
                    {
                        if (existingLength > 0)
                        {
                            if (ResumeUnsupportedWarning() == false) // warn and ask for confirmation to continue if the half downloaded file is unresumable
                            {
                                return;
                            }
                        }
                        existingLength = 0;
                        downloadResumable = false;
                    }
                    OnResumabilityChanged(new DownloadStatusChangedEventArgs(downloadResumable));
                    using (var saveFileStream = fileInfo.Open(downloadResumable ? FileMode.Append : FileMode.Create, FileAccess.Write))
                    using (var stream = response.GetResponseStream())
                    {
                        byte[] downBuffer = new byte[4096];
                        int byteSize = 0;
                        long totalReceived = byteSize + existingLength;
                        var sw = Stopwatch.StartNew();
                        while (!stop && (byteSize = stream.Read(downBuffer, 0, downBuffer.Length)) > 0)
                        {
                            saveFileStream.Write(downBuffer, 0, byteSize);
                            totalReceived += byteSize;
                            float currentSpeed = totalReceived / (float)sw.Elapsed.TotalSeconds;
                            OnProgressChanged(new DownloadProgressChangedEventArgs(totalReceived, fileSize, (long)currentSpeed));
                            pauseLock.Wait();
                            pauseLock.Release();
                        }
                        sw.Stop();
                    }
                }
                if (!stop) OnCompleted(EventArgs.Empty);
            }
            catch (WebException e)
            {
                System.Windows.MessageBox.Show(e.Message, filename);
            }
        }
        public void pause()
        {
            if (!paused)
            {
                paused = true;
                // Note this cannot block for more than a moment
                // since the download thread doesn't keep the lock held
                pauseLock.Wait();
            }
        }
        public void unpause()
        {
            if (paused)
            {
                paused = false;
                pauseLock.Release();
            }
        }
        public void StopDownload()
        {
            stop = true;
            this.unpause();  // stop waiting on lock if needed
        }
        public bool ResumeUnsupportedWarning()
        {
            var messageBoxResult = System.Windows.MessageBox.Show("When trying to resume the download , Mackerel got a response from the server that it doesn't support resuming the download. It's possible that it's a temporary error of the server, and you will be able to resume the file at a later time, but at this time Mackerel can download this file from the beginning.'n'nDo you want to download this file from the beginning?", filename, System.Windows.MessageBoxButton.YesNo);
            if (messageBoxResult == System.Windows.MessageBoxResult.Yes)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        protected virtual void OnResumabilityChanged(DownloadStatusChangedEventArgs e)
        {
            var handler = ResumablityChanged;
            if (handler != null)
            {
                handler(this, e);
            }
        }
        protected virtual void OnProgressChanged(DownloadProgressChangedEventArgs e)
        {
            var handler = ProgressChanged;
            if (handler != null)
            {
                handler(this, e);
            }
        }
        protected virtual void OnCompleted(EventArgs e)
        {
            var handler = Completed;
            if (handler != null)
            {
                handler(this, e);
            }
        }
    }
    public class DownloadStatusChangedEventArgs : EventArgs
    {
        public DownloadStatusChangedEventArgs(bool canResume)
        {
            ResumeSupported = canResume;
        }
        public bool ResumeSupported { get; private set; }
    }
    public class DownloadProgressChangedEventArgs : EventArgs
    {
        public DownloadProgressChangedEventArgs(long totalReceived, long fileSize, long currentSpeed)
        {
            BytesReceived = totalReceived;
            TotalBytesToReceive = fileSize;
            CurrentSpeed = currentSpeed;
        }
        public long BytesReceived { get; private set; }
        public long TotalBytesToReceive { get; private set; }
        public float ProgressPercentage 
        { 
            get 
            { 
                return ((float)BytesReceived / (float)TotalBytesToReceive) * 100; 
            } 
        }
        public float CurrentSpeed { get; private set; } // in bytes
        public TimeSpan TimeLeft
        {
            get
            {
                var bytesRemainingtoBeReceived = TotalBytesToReceive - BytesReceived;
                return TimeSpan.FromSeconds(bytesRemainingtoBeReceived / CurrentSpeed);
            }
        }
    }
}

Download类在一个Mackerel类中被实例化，该类为给定的下载启动下载。

using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Windows;
namespace Mackerel_Download_Manager
{
    public static class Mackerel
    {
        //Main Menu functions
        public static void ResumeDownload(string[] DownloadIDs)
        {
            foreach (var DownloadID in DownloadIDs)
            {
                var itemToResume = Downloads.DownloadEntries.Where(download => download.DownloadID == DownloadID).FirstOrDefault();
                if (itemToResume.Running == false)
                {
                    itemToResume.Running = true;
                    var download = new Download();
                    download.DownloadFile(itemToResume.DownloadLink, itemToResume.SaveTo);
                    var window = new Dialogs.DownloadProgress(itemToResume);
                    window.Show();
                    double progress = 0;
                    itemToResume.Status = string.Format("{0:0.00}%", progress);
                    Downloads.DownloadEntries.CollectionChanged += delegate 
                    { 
                        if (!itemToResume.Running) window.Close(); 
                    };
                }
            }
        }
        public static void StopDownload(string[] DownloadIDs)
        {
            foreach (var DownloadID in DownloadIDs)
            {
                var itemToStop = Downloads.DownloadEntries.Where(download => download.DownloadID == DownloadID).FirstOrDefault();
                if (itemToStop.Running == true)
                    itemToStop.Running = false;
            }
        }
        public static void StopAllDownloads()
        {
            foreach (var itemToStop in Downloads.DownloadEntries.Where(download => download.Running == true))
                itemToStop.Running = false;
        }
        public static void RemoveDownload(string[] DownloadIDs) // this method is able to delete multiple downloads
        {
            foreach (var DownloadID in DownloadIDs)
            {
                // delete from the download list
                var selectedDownload = Downloads.DownloadEntries.Where(download => download.DownloadID == DownloadID).FirstOrDefault();
                var selectedDownloadIndex = Downloads.DownloadEntries.IndexOf(selectedDownload);
                Downloads.DownloadEntries.RemoveAt(selectedDownloadIndex);
                //delete from the harddrive
                if (File.Exists(selectedDownload.SaveTo))
                    File.Delete(selectedDownload.SaveTo);
            }
            Downloads.Serialize(); // save current state of object
        }
        public static void RemoveCompletedDownloads() // this method just removes all completed downloads from Mackerel's download list (it doesn't delete them from the hard drive)
        {
            foreach (var itemToRemove in Downloads.DownloadEntries.Where(download => download.Status == "Complete").ToList())
            {
                Downloads.DownloadEntries.Remove(itemToRemove);
            }
        }
        // Context Menu
        public static void OpenDownloadProperties(string DownloadID) // Open "Download Properties" for the given download ID
        {
            var DownloadProperties = new Dialogs.Context_Menu.DownloadProperties(DownloadID);
            DownloadProperties.Owner = Application.Current.MainWindow; // so that this dialog centers to its parent window, as its window is set to WindowStartupLocation="CenterOwner"
            DownloadProperties.ShowDialog();
        }
    }
}

完整源代码在这里:https://github.com/Expenzor/mackerel-download-manager