C# 异步下载时设置用户状态

VS2008SP1

我正在使用web客户端异步下载一些文件

我有5个文件要下载

但是，我希望监视每个下载，并希望将用户状态设置为文件名，以便在ProgressCompletedEvent中检查用户状态以查看哪个文件已完成

他是我试图做的一个简短的代码片段

// This function will be called for each file that is going to be downloaded.
// is there a way I can set the user state so I know that the download 
// has been completed 
// for that file, in the DownloadFileCompleted Event? 
private void DownloadSingleFile()
{
    if (!wb.IsBusy)
    {        
        //  Set user state here       
        wb.DownloadFileAsync(new Uri(downloadUrl), installationPath);
    }
}


void wb_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
    Console.WriteLine("File userstate: [ " + e.UserState + " ]");   
}

void wb_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
    Console.WriteLine("File userstate: [ " + e.UserState + " ]");   

    double bytesIn = double.Parse(e.BytesReceived.ToString());
    double totalBytes = double.Parse(e.TotalBytesToReceive.ToString());
    double percentage = bytesIn / totalBytes * 100;

    progressBar1.Value = int.Parse(Math.Truncate(percentage).ToString());

}

---

您可以将任何对象作为第三个参数传递给DownloadFileAsync（）调用，然后将其作为userState返回。在您的情况下，只需传递文件名即可

像这样的东西怎么样：

private void BeginDownload(
    string uriString,
    string localFile,
    Action<string, DownloadProgressChangedEventArgs> onProgress,
    Action<string, AsyncCompletedEventArgs> onComplete)
{
    WebClient webClient = new WebClient();

    webClient.DownloadProgressChanged +=
        (object sender, DownloadProgressChangedEventArgs e) =>
            onProgress(localFile, e);

    webClient.DownloadFileCompleted +=
        (object sender, AsyncCompletedEventArgs e) =>
            onComplete(localFile, e);

    webClient.DownloadFileAsync(new Uri(uriString), localFile);
}

Action<string, DownloadProgressChangedEventArgs> onProgress =
    (string localFile, DownloadProgressChangedEventArgs e) =>
    {
        Console.WriteLine("{0}: {1}/{2} bytes received ({3}%)",
            localFile, e.BytesReceived,
            e.TotalBytesToReceive, e.ProgressPercentage);
    };

Action<string, AsyncCompletedEventArgs> onComplete =
    (string localFile, AsyncCompletedEventArgs e) =>
    {
        Console.WriteLine("{0}: {1}", localFile,
            e.Error != null ? e.Error.Message : "Completed");
    };

downloader.BeginDownload(
    @"http://url/to/file",
    @"/local/path/to/file",
    onProgress, onComplete);

调用两次，将得到如下输出

/路径/到/文件1：收到265/265字节（100%）
/路径/到/文件1：已完成
/路径/到/文件2：收到2134/2134字节（100%）

---

/路径/to/file2:Completed

client.UploadFileCompleted+=新的UploadFileCompletedEventHandler（UploadFileCallback）；UploadFileAsync（uri，“STOR”、源文件、文件名）；私有void UploadFileCallback（对象发送方，UploadFileCompletedEventArgs e）{MessageBox.Show（e.UserState.ToString（））；…}

private void BeginDownload(string uriString, string localFile)
{
    WebClient webClient = new WebClient();

    webClient.DownloadProgressChanged +=
        (object sender, DownloadProgressChangedEventArgs e) =>
            Console.WriteLine("{0}: {1}/{2} bytes received ({3}%)",
                localFile, e.BytesReceived,
                e.TotalBytesToReceive, e.ProgressPercentage);

    webClient.DownloadFileCompleted +=
        (object sender, AsyncCompletedEventArgs e) =>
            Console.WriteLine("{0}: {1}", localFile,
                e.Error != null ? e.Error.Message : "Completed");

    webClient.DownloadFileAsync(new Uri(uriString), localFile);
}