I am trying to implement a PDF generation utility which will take a URL and then convert the URL into a PDF. When I do this without threading it runs fine, but I would like to thread the process to speed it up. I am implementing a thread pool inside of a foreach loop that iterates through each URL that needs that needs to be converted, and the thread pool calls the EO pdf code to create the pdf file. When it gets to the ConvertURL call, all threads freeze up for a while until they finally throw an exception stating that I need to increase the MaxConcurrentTaskCount. This happens even if only 2 threads are running, and even if i set the MaxConcurrentTaskCount to a high number. Is there something I am missing here that needs to be done for this to work with threading?

I'm not sure if posting my code will be much help. This utility is used by an application to generate of PDF of the page the user is viewing, and this is done by passing the URL for this page along with other parameters to the utility. To have you be able to use it would mean I would have to rewrite some of the code for it to work outside of its current environment.

The strange thing is if I only have one thread run it works fine, but as soon as more than 1 thread tries to access the ConvertURL function it fails. If I debug this process all threads that are running fail at this same spot. I had initially tried this with a Parallel foreach loop, but was facing issues with concurrency and using a List, so I decided to use a ThreadPool. When using the Parellel foreach loop the conversion was working fine, it did not hang at the convertUrl call. Is there an issue with using a thread pool and calling the convertUrl method?

Below is my code - When this is run the threads will hang at the ConvertUrl call -

//Starts the thread pool for each url that needs to be converted.
foreach (IDictionary dictionary in parameters2)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(delegate(object state) { GeneratePDF(dictionary,parameters,directory); }));
}


//Generate PDF code
foreach (var dict in dictionary.Values)
{
Hashtable param = Utility.Cast<Hashtable>(dict);

urlForPdf = param["UrlForPdf"].ToString();
DealerName = param["DealerName"].ToString();

try
{
HtmlToPdf.Options.OutputArea = new RectangleF(0.5f, 0.5f, PdfPageSizes.A4.Height, PdfPageSizes.A4.Width);
HtmlToPdf.Options.PageSize = new SizeF(PdfPageSizes.A4.Height + 1, PdfPageSizes.A4.Width + 1);
HtmlToPdf.Options.RepeatTableHeaderAndFooter = false;
HtmlToPdf.Options.AutoFitX = HtmlToPdfAutoFitMode.ScaleToFit;

PdfDocument PdfDoc = new PdfDocument();
HtmlToPdf.ConvertUrl(urlForPdf, PdfDoc);

documents.Add(PdfDoc);
}
catch (System.Exception exc)
{
System.IO.File.WriteAllText(String.Concat(directory, "\\Exception.txt"), exc.ToString());
//Add some better exception logic here. Return error page or something.
throw;
}
}