DownloadFileCompleted / DownloadProgressChanged事件不起作用

Question

I have a background worker (as seen below) with DownloadFileCompleted/DownloadProgressChanged events. After several hours of testing and a lot of research, I couldn't get it to work. The file downloads successfully but the events don't run. I looked at a lot of documentation pages and searched for this issue here, but they don't seem to match my case... Would appreciate if someone could help me out on this one!

    private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
    {
            WebClient client = new WebClient();
            client.DownloadProgressChanged += new DownloadProgressChangedEventHandler (webClient_DownloadProgressChanged);
            client.DownloadFileCompleted += new AsyncCompletedEventHandler  (webClient_DownloadFileCompleted);

            client.DownloadFileAsync(new Uri(myUri), path);

        }
    }

    void webClient_DownloadFileCompleted(object s, AsyncCompletedEventArgs e)
    {
        Debug.WriteLine("Download completed!");
    }
    void webClient_DownloadProgressChanged(object s, DownloadProgressChangedEventArgs e)
    {
        Debug.WriteLine(e.BytesReceived);
    }

Answer 1

There must be something else wrong with your code as running effectively that same code, it works fine.

Are you sure your program is simply not finished and closing before the work is done as a BackgroundWorker won't keep your application alive.

Here is my example, with a foreground Thread to keep the application alive until done

using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Net;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            new Thread(() =>
            {
                var client = new WebClient();
                client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
                client.DownloadFileCompleted += new AsyncCompletedEventHandler(webClient_DownloadFileCompleted);

                client.DownloadFileAsync(new Uri("https://speed.hetzner.de/100MB.bin"), @"C:\Users\Luke\Desktop\100mb.bin");
            }).Start();
        }

        private static void webClient_DownloadFileCompleted(object s, AsyncCompletedEventArgs e)
        {
            Debug.WriteLine("Download completed!");
        }
        private static void webClient_DownloadProgressChanged(object s, DownloadProgressChangedEventArgs e)
        {
            Debug.WriteLine(e.BytesReceived);
        }
    }
}