c# - 为什么我收到错误 Cannot await 'void' ？

Question

private Queue<string> _downloadUrls = new Queue<string>();

        private void downloadFile(IEnumerable<string> urls)
        {
            foreach (var url in urls)
            {
                _downloadUrls.Enqueue(url);
            }

            DownloadFile();
        }

        private async Task DownloadFile()
        {
            if (_downloadUrls.Any())
            {
                WebClient client = new WebClient();
                client.DownloadProgressChanged += ProgressChanged;
                client.DownloadFileCompleted += Completed;

                var url = _downloadUrls.Dequeue();
                string FileName = url.Substring(url.LastIndexOf("/") + 1,
                            (url.Length - url.LastIndexOf("/") - 1));

                await client.DownloadFileAsync(new Uri(url), "C:\\Test4\\" + FileName);
                return;
            }
        }

错误在线:

await client.DownloadFileAsync(new Uri(url), "C:\\Test4\\" + FileName);

我该如何解决这个错误？为什么会发生？我给出了我认为的所有细节。

我添加了可能需要的其余代码。

Answer 1

WebClient.DownloadFileAsync 是一种基于事件的 API，早于任务和异步/等待。您需要等待 WebClient.DownloadFileTaskAsync。