c# - DownloadFileAsync 不下载文件

Question

我正在尝试编写一个简单的应用程序，它可以从网络上下载一个文件。

class Program
{
    static void Main(string[] args)
    {
        WebClient client = new WebClient();
        Uri uri = new Uri("http://download.thinkbroadband.com/100MB.zip");

        // Specify that the DownloadFileCallback method gets called
        // when the download completes.
        client.DownloadFileCompleted += new AsyncCompletedEventHandler(DownloadFileCallback2);
        // Specify a progress notification handler.
        client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgressCallback);
        client.DownloadFileAsync(uri, "serverdata.txt");

        Console.WriteLine("Download successful.");

    }
    private static void DownloadProgressCallback(object sender, DownloadProgressChangedEventArgs e)
    {
        // Displays the operation identifier, and the transfer progress.
        Console.WriteLine("{0}    downloaded {1} of {2} bytes. {3} % complete...",
            (string)e.UserState,
            e.BytesReceived,
            e.TotalBytesToReceive,
            e.ProgressPercentage);
    }
    private static void DownloadFileCallback2(object sender, AsyncCompletedEventArgs e)
    {
        // Displays the operation identifier, and the transfer progress.
        Console.WriteLine("Download complete");
    }
}

我在这一行中放置了断点:Console.WriteLine("Download complete"); 但它从未命中。程序创建空的 serverdata.txt 文件。我在控制台中没有收到有关 DownloadProgressCallback 下载百分比的更新。我做错了什么？

Answer 1

我没试过，但你可以尝试使用 IsBusy属性:

while(client.IsBusy)
     Thread.Sleep(1000);

Console.WriteLine("Download successful.");

或者，使用 WebClient.DownloadFileTaskAsync如果您使用的是 .NET 4.5，则方法

client.DownloadFileTaskAsync(uri, "serverdata.txt").Wait();
Console.WriteLine("Download successful.");