UWP BackgroundDownloader 即使在 PC 上也会冻结答案

【问题标题】：UWP BackgroundDownloader freezes even on PCUWP BackgroundDownloader 即使在 PC 上也会冻结
【发布时间】：2017-05-26 12:17:04
【问题描述】：

string url = "http://any_urls";
    MediaPlayer player = new MediaPlayer();

    public MainPage()
    {
        InitializeComponent();

        Debug.WriteLine("Download started");
        var file = Download().Result; // <-- Here's where it stucks
        Debug.WriteLine("Download finished");

        player.Source = MediaSource.CreateFromStorageFile(file);
        player.Play();
    }

    private async Task<StorageFile> Download()
    {
        StorageFile destinationFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(
            "data.mp3", CreationCollisionOption.GenerateUniqueName);
        BackgroundDownloader downloader = new BackgroundDownloader();
        DownloadOperation download = downloader.CreateDownload(new Uri(url), destinationFile);
        await download.StartAsync();
        return destinationFile;
    }

我在 PC 和手机上都进行了测试，它们都冻结了整个过程。任何人都可以解决这个问题，或者有什么好的替代方法吗？

【问题讨论】：

标签： c# download background uwp

【解决方案1】：

开始下载时忘记调用“AsTask”方法。

不能有异步构造函数。

public MainPage()
{
    this.InitializeComponent();
}

private async void Page_Loaded(object sender, RoutedEventArgs e)
{
    Debug.WriteLine("Download started");
    var file = await DownloadAsync();
    Debug.WriteLine("Download finished");

    player.Source = MediaSource.CreateFromStorageFile(file);
    player.Play();
}

private async Task<StorageFile> DownloadAsync()
{
    StorageFile destinationFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(
        "data.mp3", CreationCollisionOption.GenerateUniqueName);
    BackgroundDownloader downloader = new BackgroundDownloader();
    DownloadOperation download = downloader.CreateDownload(new Uri(url), destinationFile);
    await download.StartAsync().AsTask();
    return destinationFile;
}

【讨论】：