BrowserFetcher exit application using await

Question

I'm using Puppeteer-Sharp to download the html of a site, I created a method called GetHtml which return a string that contains the site content. The problem is that when I call the line await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultRevision);

The application exit without any errors, this is my code:

public class Program
{
    public static void Main(string[] args)
    {
        try
        {
            new FixtureController().AddUpdateFixtures();
        }
        catch (Exception ex)
        {
            new Logger().Error(ex);
        }
    }
}

public async Task AddFixtures()
{
    int monthDays = DateTime.DaysInMonth(DateTime.Now.Year, DateTime.Now.Month);
    var days = Enumerable.Range(1, monthDays).Select(x => x.ToString("D2")).ToArray();

    HtmlDocument doc = new HtmlDocument(); //this is part of Htmlagilitypack library

    foreach (var day in days)
    {
        //Generate url for this iteration
        Uri url = new Uri("somesite/" + day);

        var html = await NetworkHelper.GetHtml(url);
        doc.LoadHtml(html);
    }
}

so each foreach iteration will generate an url which download the data, and the method GetHtml should return the html but the application exit (without errors) when reach var html = .., this is the code of GetHtml:

    public static async Task<string> GetHtml(Uri url)
    {
        try
        { 
            //here the crash
            await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultRevision);
        }
        catch (Exception e)
        {
             //No breakpoint point firing
        }

        await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultRevision);

        var browser = await Puppeteer.LaunchAsync(new LaunchOptions
        {
            Headless = true
        });

        using (Page page = await browser.NewPageAsync())
        {
            await page.GoToAsync(url.ToString());
            return await page.GetContentAsync();
        }
    }

score 3 · Accepted Answer · answered Jul 26 '18 at 12:31

Your main method does not wait for the result of your async call. The main method exits, closing the application. To fix it you need to wait for the async method to finish.

If you're using C# 7.1 or newer you can use async Main:

public class Program
{
    public static async void Main()
    {
        await TestAsync();
    }

    private static async Task TestAsync() 
    {
        await Task.Delay(5000);
    }
}

Otherwise you need to wait synchronously:

public class Program
{
    public static void Main()
    {
        TestAsync().GetAwaiter().GetResult();
    }

    private static async Task TestAsync() 
    {
        await Task.Delay(5000);
    }
}

Yep, this seems to working, thanks for your help, have a good day :) — Charanoglu, Jul 26 '18 at 12:35

BrowserFetcher exit application using await

1 Answers1