Question

I’m using the WkHtmlToXSharp wrapper library in my project to generate PDF file from HTML.

I was using this library a lot of times in different PCs and, suddenly, I came across the following problem:

System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
at WkHtmlToXSharp.WkHtmlToPdfConverter.wkhtmltopdf_convert(IntPtr converter)
at WkHtmlToXSharp.WkHtmlToPdfConverter.Convert(String inputHtml)
at WkHtmlToXSharp.WkHtmlToPdfConverter.Convert()
at WkHtmlToXSharp.MultiplexingConverter.b_8()
— End of inner exception stack trace —
at Sanford.Threading.DelegateQueue.EndInvoke(IAsyncResult result)
at Sanford.Threading.DelegateQueue.Invoke(Delegate method, Object[] args)
at WkHtmlToXSharp.MultiplexingConverter.Convert()

This seems to be a common problem with this library (I’ve found some feedback on the web about it – however no fix was provided). BTW, in my case it happens somewhat randomly. I was not experiencing this problem in other dev machines. I wonder if somebody has a fix for it. I also wonder if this is a problem with the wrapper library, if with the WkHtmlToPDF library itself.

Any suggestion? I’m also open to use another converter, as long as it is free and stable and, if possible, without spawning a new process. It must work properly and stable in all Windows versions and do a decent job converting (the HTML to be converted is fixed – contains a few pics and tables and basic CSS).

Answer 1

I would suggest an alternate route: simply use wkhtmltopdf.exe directly, building your own wrapper. They are not very complicated if you have control of the input and then you know exactly how to update it and how the options work. I’ve never encountered with that problem when using wkhtmltopdf directly (on Win7, Win server 2008 r2, Ubuntu and CentOS). They do spawn process for every conversion though.

For an example, check out the Derp class in another answer of mine regarding wkhtmltopdf. Or try something like the untested code below (your true code will be more complicated, this is just a demo/POC).

var pi = new ProcessStartInfo(@"c:\wkhtmltopdf\wkhtmltopdf.exe");
pi.CreateNoWindow = true;
pi.UseShellExecute = false;
pi.WorkingDirectory = @"c:\wkhtmltopdf\";
pi.Arguments = "http://www.google.com gogl.pdf";

using (var process = Process.Start(pi))
{
    process.WaitForExit(99999);
    Debug.WriteLine(process.ExitCode);
}