How to use MessageException method of PuppeteerSharp.MessageException class

I made a stupid typo when searching answers from other people. Actually, it was simple. The launch option has some wrong text, delete the http:// is enough, since I am using direct IP address. So the correct syntax is:

rivate static readonly LaunchOptions puppeteer_launchOptions = new LaunchOptions 
{
Headless = false,
IgnoreHTTPSErrors = true,
    Args = new [] {
        "--proxy-server=1.2.3.4:5678",
        "--no-sandbox",
        "--disable-infobars",
        "--disable-setuid-sandbox",
        "--ignore-certificate-errors",
    },

};

By the way, --disable-infobars seems not working since 1.19.0 until 1.20.0; I always see the information: Chrome is being controlled by automated test software. I remember someone said since 1.19.0 Google Chrome changed something, so --disable-infobars not working, but he also provide some example how to disable the warning, but his method did NOT include PuppeteerSharp, Puppeteer was included. Now, I can't figure it out yet.
Hope my question can help some other people. It is just a typo, not a big issue!

Change your Window_Loaded event method to async and do an await on the Init method, Event Handler methods are an exception. using async void instead of async Task is ok in this scenario. - Reference (Should I avoid 'async void' event handlers?):

private async void Window_Loaded(object sender, RoutedEventArgs e) 
{  
   await Handler.Init(Handler);
}

Try to use "innerText" except "textContent".

var strValueEst = await page.EvaluateFunctionAsync(
  "()=>document.querySelector('#path > path > nbPoints').innerText"
);

I found a solution: If the pages will be created in the same scope as their browser instance, then the pages will be created as expected, otherwise Task.Run() will be stuck due to NewPageAsync() method.

Bad behaviour:

Task[] Tasks = new Task[1];
Browser browser = await Puppeteer.LaunchAsync
(
    new LaunchOptions
    {
        Headless = true,
        ExecutablePath = "Chromium\\chrome.exe"
    }
);
for (int i = 0; i < Tasks.Length; i++)
{
    int ThreadNumber = i;
    Tasks[i] = Task.Run(async () =>
    {
       Page page = await browser.NewPageAsync(); //stucks
    });
}

Task.WaitAll(Tasks);

As expected:

Task[] Tasks = new Task[1];
for (int i = 0; i < Tasks.Length; i++)
{
    int ThreadNumber = i;
    Tasks[i] = Task.Run(async () =>
    {
       Browser browser = await Puppeteer.LaunchAsync
       (
           new LaunchOptions
           {
                Headless = true,
               ExecutablePath = "Chromium\\chrome.exe"
           }
       );
       Page page = await browser.NewPageAsync(); //creates as expected
    });
}

Task.WaitAll(Tasks);

Anyway this is not the best solution because I have to create browsers for async tasks rather than using one browser for all async tasks. Hope someone can explain that. Thanks everyone for helping!

System.ValueTuple was added in .NET 4.7. Upgrading your project to 4.7 would be easiest.

If you can't, but your project is targetting a version 4.5+ but less than 4.7, then you can install the System.ValueTuple NuGet package. If you run into any trouble there, see this answer.

Got it:
var localStorage = await page.EvaluateFunctionAsync<Dictionary<string, string>>("async () => Object.assign({}, window.localStorage)");

This code will load www.kayak.com with no images:

using (var browser = await Puppeteer.LaunchAsync(new LaunchOptions { Headless = false }))
using (var page = await browser.NewPageAsync())
{
    await page.SetRequestInterceptionAsync(true);

    // disable images to download
    page.Request += (sender, e) =>
    {
        if (e.Request.ResourceType == ResourceType.Image)
            e.Request.AbortAsync();
        else
            e.Request.ContinueAsync();
    };
    await page.GoToAsync("https://www.kayak.com");
    Console.ReadLine();
}

I think you're looking for something like Google's Puppeteer or given your C# tag, perhaps the .NET port Puppeteer Sharp.

... library which provides a high-level API to control Chrome or Chromium over the DevTools Protocol. Puppeteer runs headless by default, but can be configured to run full (non-headless) Chrome or Chromium.

How to use PuppeteerSharp inside an UWP App?

PuppeteerSharp does not support in UWP, You could check PuppeteerSharp source code to verify this. This is DownloadsFolder = Path.Combine(Directory.GetCurrentDirectory(), ".local-chromium") and matched path is "{AppRoot}\bin\x86\Debug\AppX.local-chromium". In the following code we call Create method in it, but above path is read-only in UWP.

    public async Task<RevisionInfo> DownloadAsync(int revision)
    {
        var url = GetDownloadURL(Platform, DownloadHost, revision);
        var zipPath = Path.Combine(DownloadsFolder, $"download-{Platform.ToString()}-{revision}.zip");
        var folderPath = GetFolderPath(revision);

        if (new DirectoryInfo(folderPath).Exists)
        {
            return RevisionInfo(revision);
        }

        var downloadFolder = new DirectoryInfo(DownloadsFolder);
        if (!downloadFolder.Exists)
        {
            downloadFolder.Create();
        }

        if (DownloadProgressChanged != null)
        {
            _webClient.DownloadProgressChanged += DownloadProgressChanged;
        }
        await _webClient.DownloadFileTaskAsync(new Uri(url), zipPath).ConfigureAwait(false);

        if (Platform == Platform.MacOS)
        {
            //ZipFile and many others unzip libraries have issues extracting .app files
            //Until we have a clear solution we'll call the native unzip tool
            //https://github.com/dotnet/corefx/issues/15516
            NativeExtractToDirectory(zipPath, folderPath);
        }
        else
        {
            ZipFile.ExtractToDirectory(zipPath, folderPath);
        }

        new FileInfo(zipPath).Delete();

        var revisionInfo = RevisionInfo(revision);

        if (revisionInfo != null && GetCurrentPlatform() == Platform.Linux)
        {
            LinuxSysCall.Chmod(revisionInfo.ExecutablePath, LinuxSysCall.ExecutableFilePermissions);
        }
        return revisionInfo;
    }