How to use CoverageEntry class of PuppeteerSharp.PageCoverage package

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);
    }
}

The problem is how the CSSStyleDeclaration is serialized. If that´s how Chromium decides to serialize that object there is nothing we can do there.

But, we can try to solve that from javascript using EvaluateFunctionAsync.

foreach (var handle in elementHandles)
{
  var style = await page.EvaluateFunctionAsync<Dictionary<string, string>>(
    "e => Object.entries(e.style).filter(i => isNaN(i[0]) && i[1]).map(i => { return { [i[0]] : i[1]}}).reduce((acc, cur) => { return {...acc, ...cur}}, {})", handle);
  var output = style.ToString();
}

Let's take a look at the javascript expression

e=> //We send the HTML element instead of the style property
  Object.entries(e.style) //We get all the property/value pairs from the CSSStyleDeclaration object
    // We want to exclude number properties (like 0,1,2) and empty values
    .filter(i => isNaN(i[0]) && i[1]) 
    //We turn them into objects
    .map(i => { return { [i[0]] : i[1]}})
    //We merge them into one single object that will be returned to C#
    .reduce((acc, cur) => { return {...acc, ...cur}}, {})

I found a few issues in your code. First a few small errors in your javascript code: you don't need to async and an extra brackets.

var jsCode = @"() => {
  const element = document.querySelector('.productDetail svg[viewbox=""0 0 16 16""]');
  return window.getComputedStyle(element).getPropertyValue('color');
}";

You shouldn't turn those flags on unless you get stuck :)

• EnqueueAsyncMessages was created for cases where your code is not async all the way. I honestly dislike that flag.
• EnqueueTransportMessages is recommended on .NET Framework code because the websocket library behaves differently there.

Regarding ResourceTypes, ResourceType.Image comes from Chrome and ResourceType.Img comes from Firefox.

That's the right way, for example:

var six = await page.EvaluateFunctionAsync<int>("async () => await Promise.resolve(6)");

That's the right way, for example:

var six = await page.EvaluateFunctionAsync<int>("async () => await Promise.resolve(6)");

Either give your submit button an id property and use the #submit selector you previously tried:

<button id="submit" type="submit" class="btn btn-danger btn-lg btn-block">Login</button>

Or use form button[type=submit] as selector.

You could use a using block for that:

public static async Task<string> renderHtmlAsync(string url2)
{
    await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultChromiumRevision);
    using (Browser browser = await Puppeteer.LaunchAsync(new LaunchOptions
    {
        Headless = true
    }))
    {
        var page = await browser.NewPageAsync();
        page.DefaultTimeout = 0;
        var navigation = new NavigationOptions
        {
            Timeout = 0,
            WaitUntil = new[] {
                    WaitUntilNavigation.DOMContentLoaded }
        };
        await page.GoToAsync(url2, navigation);
        var content = page.GetContentAsync();

        return await content;
    }
}

This works like:

var myObject = new DispoableObject();
try
{
    // insert code
    return result;
}
finally
{
    myObject.Dispose();
}

The code in the finally is always executed, even when an exception is thrown inside the try block.

From the examples in the docs, it looks like you have to do this:

// select the tag first
var element = await _page.QuerySelectorAsync("h1 > strong > a");

// then get the attribute
var url = await element.EvaluateFunctionAsync<string>("e => e.getAttribute('href')");
// OR
var url = await _page.EvaluateFunctionAsync<string>("e => e.getAttribute('href')", element);
// OR
var url = await (await element.GetPropertyAsync("href")).JsonValueAsync<string>();

// OR all in one
var url = await _page.EvaluateExpressionAsync<string>($"document.querySelector({"'h1 > strong > a'"}).getAttribute('href')");

You gotta apply this to the value of a select option, of course. Probably 'value' instead of 'href' and the correct selector.