是否可以“加入”？ DownloadStringAsync 操作？

发布于 2024-10-27 19:50:45 字数 595 浏览 0 评论 0原文

我有这样的代码：

public static String Download(string address) {
    WebClient client = new WebClient();
    Uri uri = new Uri(address);

    // Specify a progress notification handler.
    client.DownloadProgressChanged += (_sender, _e) => {
        // 
    };

    // ToDo: DownloadStringCompleted event

    client.DownloadStringAsync(uri);
}

我可以以某种方式加入此异步请求，而不是在下载完成时在 DownloadStringCompleted 事件处理程序中执行其余代码吗？它将被放置在另一个线程中（这样做是为了让我可以访问下载进度）。我知道 DownloadStringAsync 可以采用第二个参数；手册中名为 userToken 的对象。这能有用吗？谢谢你，

原文

I have this code:

public static String Download(string address) {
    WebClient client = new WebClient();
    Uri uri = new Uri(address);

    // Specify a progress notification handler.
    client.DownloadProgressChanged += (_sender, _e) => {
        // 
    };

    // ToDo: DownloadStringCompleted event

    client.DownloadStringAsync(uri);
}

Instead of having the rest of my code execute in the DownloadStringCompleted event handler when the download is complete, can I somehow Join this Async request? It will be housed in another thread (doing it this way so I have access to the download progress). I know that DownloadStringAsync can take a second parameter; an object called userToken in the manual. Could this be of use? Thank you,

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旧城烟雨 2024-11-03 19:50:45

您可以使用手动重置事件：

class Program
{
    static ManualResetEvent _manualReset = new ManualResetEvent(false);

    static void Main()
    {
        WebClient client = new WebClient();
        Uri uri = new Uri("http://www.google.com");

        client.DownloadProgressChanged += (_sender, _e) =>
        {
            //
        };

        client.DownloadStringCompleted += (_sender, _e) => 
        {
            if (_e.Error == null)
            {
                // do something with the results
                Console.WriteLine(_e.Result);
            }
            // signal the event
            _manualReset.Set();
        };

        // start the asynchronous operation
        client.DownloadStringAsync(uri);

        // block the main thread until the event is signaled
        // or until 30 seconds have passed and then unblock
        if (!_manualReset.WaitOne(TimeSpan.FromSeconds(30)))
        {
            // timed out ...
        }
    }
}

You could use a manual reset event:

class Program
{
    static ManualResetEvent _manualReset = new ManualResetEvent(false);

    static void Main()
    {
        WebClient client = new WebClient();
        Uri uri = new Uri("http://www.google.com");

        client.DownloadProgressChanged += (_sender, _e) =>
        {
            //
        };

        client.DownloadStringCompleted += (_sender, _e) => 
        {
            if (_e.Error == null)
            {
                // do something with the results
                Console.WriteLine(_e.Result);
            }
            // signal the event
            _manualReset.Set();
        };

        // start the asynchronous operation
        client.DownloadStringAsync(uri);

        // block the main thread until the event is signaled
        // or until 30 seconds have passed and then unblock
        if (!_manualReset.WaitOne(TimeSpan.FromSeconds(30)))
        {
            // timed out ...
        }
    }
}

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弥枳 2024-11-03 19:50:45

我的第一个想法是使用 DownloadString，DownloadStringAsync。但是，似乎您必须使用异步方法来获取进度通知。好吧，这没什么大不了的。只需订阅 DownloadStringCompleted 并使用简单的等待像 ManualResetEventSlim 一样处理以阻止直到完成。

需要注意的是，我不确定 DownloadStringAsync 是否会发出进度通知。根据 MSDN，DownloadProgressChanged 与某些相关异步方法，但不是 DownloadStringAsync。