Cwait控制台应用程序代码在等待之后不执行

async-await c# html-agility-pack html-parsing

我正在尝试创建一个webscraper,从html文件中获取css / js / images的所有下载链接。

问题

第一个断点确实命中,但第二个断点没有击中“继续”。

Visual Studio中的图片

我正在谈论的代码:

  private static async void GetHtml(string url, string downloadDir)
    {

        //Get html data, create and load htmldocument 
        HttpClient httpClient = new HttpClient();

        //This code gets executed
        var html = await httpClient.GetStringAsync(url);

        //This code not
        Console.ReadLine();
        var htmlDocument = new HtmlDocument();
        htmlDocument.LoadHtml(html);

        //Get all css download urls
        var linkUrl = htmlDocument.DocumentNode.Descendants("link")
            .Where(node => node.GetAttributeValue("type", "")
            .Equals("text/css"))
            .Select(node=>node.GetAttributeValue("href",""))
            .ToList();

        //Downloading css, js, images and source code
        using (var client = new WebClient())
        {
            for (var i = 0; i <scriptUrl.Count; i++)
            {

                    Uri uri = new Uri(scriptUrl[i]);
                    client.DownloadFile(uri,
                    downloadDir + @"\js\" + uri.Segments.Last());

            }
        }

编辑

我从这里调用getHtml方法:

    private static void Start()
    {
        //Create a list that will hold the names of all the subpages
        List<string> subpagesList = new List<string>();

        //Ask user for url and asign that to var url, also add the url to the url list
        Console.WriteLine("Geef url van de website:");
        string url = "https://www.hethwc.nl";


        //Ask user for download directory and assign that to var downloadDir
        Console.WriteLine("Geef locatie voor download:");
        var downloadDir = @"C:\Users\Daniel\Google Drive\Almere\C# II\Download tests\hethwc\";

        //Download and save the index file
        var htmlSource = new System.Net.WebClient().DownloadString(url);
        System.IO.File.WriteAllText(@"C:\Users\Daniel\Google Drive\Almere\C# II\Download tests\hethwc\index.html", htmlSource);

        // Creating directories 
        string jsDirectory = System.IO.Path.Combine(downloadDir, "js");
        string cssDirectory = System.IO.Path.Combine(downloadDir, "css");
        string imagesDirectory = System.IO.Path.Combine(downloadDir, "images");

        System.IO.Directory.CreateDirectory(jsDirectory);
        System.IO.Directory.CreateDirectory(cssDirectory);
        System.IO.Directory.CreateDirectory(imagesDirectory);

        GetHtml("https://www.hethwc.nu", downloadDir);
    }

专家解答

你是怎么称呼GetHtml ?据推测,这是来自同步Main方法,并且您没有任何其他非工作线程在运行(因为您的主线程退出):进程将终止。就像是:

static void Main() {
    GetHtml();
}

以上将在GetHtml返回并且Main方法结束后立即终止该过程,该方法将在第一个未完成的await点处。

在当前的C#版本(C#7.1以后)中,您可以创建一个async Task Main()方法,只要您更改GetHtml以返回Task ,就可以正确await GetHtml方法:

async static Task Main() {
    await GetHtml();
}


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许可下: CC-BY-SA with attribution
不隶属于 Stack Overflow