Puppeteer LaunchAsync throwing exception - puppeteer-sharp

Question

I have an existing ASPNET Web Application. The front end is HTML/JavaScript and the backend is WebAPI 2. We have been using NRECO.PDFGenerator to drop PDFs to the users, this uses a the QT browser and debugging is becoming a chore. I found PuppeteerSharp and figured I'd give it a try.
I installed the libs using nuget, added an Async method to one of my Web Api Controllers but when I call it the LaunchAsync method just crashed.
[Route("api/pdf/v2/download")]
public IHttpActionResult V2Download([FromBody] Models.PDF.List _pdf) {
Models.Message.Response _return = new Models.Message.Response();
_return.Message = "Success!";
_return.Now = DateTime.Now;
try
{
string[] argu = null;
Meh(argu);
}
catch (Exception ex)
{
_return.Message = ex.Message;
_return.Severity = 3;
}
return Ok(_return);
}
public static async Task Meh(string[] args)
{
var options = new LaunchOptions
{
Headless = true,
Args = new[] {"--no-sandbox" }
};
Debug.WriteLine("Downloading chromium");
await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultRevision);
Debug.WriteLine("Navigating google");
using (var browser = await Puppeteer.LaunchAsync(options))
using (var page = await browser.NewPageAsync())
{
Debug.WriteLine("Navigating to page");
await page.GoToAsync("http://www.google.com");
Debug.WriteLine("Generating PDF");
await page.PdfAsync(Path.Combine(Directory.GetCurrentDirectory(), "google.pdf"));
Debug.WriteLine("Export completed");
if (!args.Any(arg => arg == "auto-exit"))
{
Console.ReadLine();
}
}
}
I'm not sure where to go from here. This is the console output. There's more...
Navigating google
The thread 0x3418 has exited with code 0 (0x0).
Exception thrown: 'System.NullReferenceException' in System.Web.dll
Exception thrown: 'System.NullReferenceException' in mscorlib.dll
The project is using framework 4.7.2
Solution
Everything that touches the Async method needs to also be Async. Also, Passing null args will cause problems as well.
Here's a code sample.
//[Authorize]
[Route("api/pdf/v2/download")]
public async Task<IHttpActionResult> V2Download([FromBody] Models.PDF.List _pdf) {
Models.Message.Response _return = new Models.Message.Response();
_return.Message = "Success!";
_return.Now = DateTime.Now;
try
{
string[] argu = { };
await Meh(argu);
}
catch (Exception ex)
{
_return.Message = ex.Message;
_return.Severity = 3;
}
return Ok(_return);
}
public static async Task Meh(string[] args)
{
var options = new LaunchOptions
{
Headless = true
};
Debug.WriteLine("Downloading chromium");
await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultRevision);
Debug.WriteLine("Navigating google");
using (var browser = await Puppeteer.LaunchAsync(options))
using (var page = await browser.NewPageAsync())
{
Debug.WriteLine("Navigating to page");
await page.GoToAsync("http://www.google.com");
Debug.WriteLine("Generating PDF");
await page.PdfAsync(Path.Combine(Directory.GetCurrentDirectory(), "google.pdf"));
Debug.WriteLine(Path.Combine(Directory.GetCurrentDirectory(), "google.pdf"));
Debug.WriteLine("Export completed");
if (!args.Any(arg => arg == "auto-exit"))
{
Console.ReadLine();
}
}
}