如何在没有AsyncEx库的情况下调用anglesharp异步方法？

Question

With AngleSharp , to load HTML page and wait until all stylesheets are downloaded (if required) and all scripts are ready to be parser executed, I do this

    public sealed class WebReader
    {
        private IDocument _ashDocument;

        public async Task Load(string Url)
        {
            var config = Configuration.Default.WithDefaultLoader().WithJavaScript().WithCss();
            var context = BrowsingContext.New(config);
            _ashDocument = await context.OpenAsync(Url);
        }

        public IEnumerable<string> getImage()
        {
            return  _ashDocument.QuerySelectorAll("img").Select(n => n.Attributes["src"].Value);
        }
    }

    static void Main(string[] args)
    {
        WebReader wReader = new WebReader();           
        AsyncContext.Run((Action)(async () =>
        {
            await wReader.Load("http://blogs.msdn.com/b/dotnet/");
        }));
        IEnumerable<string> imageUrls = wReader.getImage();
        foreach (string url in imageUrls)
        {
            Console.WriteLine(url);
        }

        Console.ReadKey();
    }

AsyncContext is a part of AsyncEx library.

Is it possible to do the same thing without AsyncEx library?

Answer 1

Is it possible to do the same thing without AsyncEx library?

Not inside a console application. The whole point of AsyncContext is to allow you to await a method in Main , which itself isn't async (and can't be). The only alternative is to block the task. Additionaly, as @StephanCleary notes, the continuation inside the context will resume on a single thread, instead of an arbitrary thread pool thread.

Without it, it would simply be:

static void Main(string[] args)
{
    WebReader wReader = new WebReader();           
    wReader.Load("http://blogs.msdn.com/b/dotnet/")).Wait();
    IEnumerable<string> imageUrls = wReader.getImage();
    foreach (string url in imageUrls)
    {
        Console.WriteLine(url);
    }
}

There are rare cases when blocking with Task.Wait is ok, this is one of them.

Side note - Async methods should be marked with the Async postfix, hence you should use LoadAsync . Also, .NET method naming conventions are Pascal case, not camel case.

Answer 2

Indeed you can:

static void Main(string[] args)
{
    DoWork();
    Console.ReadKey();
}

static async void DoWork()
{
    WebReader wReader = new WebReader();           
    await wReader.Load("http://blogs.msdn.com/b/dotnet/");
    IEnumerable<string> imageUrls = wReader.getImage();
    foreach (string url in imageUrls)
    {
        Console.WriteLine(url);
    }
}

This will do exactly the same, the only difference is the readkey is being executed while the DoWork downloads it's data, if this side effect is not an inconvenient then you're good.

Else, you can use a sync event (ManualResetEvent, AutoResetEvent, etc) to wait until the work has been done.