ClickOnce Applications fail in certain circumstances

[jackmang]

I spent hours trying to find a .Net 8 compatible way to print an existing PDF file that didn't require licensing. Something I thought was super simple, but isn't. This is where I ended up and I came here with low expectations. I am now very pleased that it works perfectly for my needs (Windows environment, .Net (Core)). Thank you for this.

I did run into an issue that required me to manually patch the code with a minor change. My application utilizes Microsoft ClickOnce for deployment, and in my case I am deploying framework Independent. It seems with ClickOnce, when you build framework independent, it puts your dependency files into the application folder (.\pdfium.dll) and not into a separate .\runtimes\win-x64\native\pdfium.dll folder as assumed in the code. This triggers the following exception:

throw new FileNotFoundException($"Native Library not found in path {path} or {Path.Combine(assemblySearchPath, fileName)}. " +
	$"Verify you have included the native Pdfium library in your application, " +
	$"or install the default libraries with the bblanchon.PDFium NuGet.");

I have a fix that seems to work for me. Unfortunately, I'm not a git user, so creating a pull request is a big ask, but I thought I'd share what worked for me without breaking the original code.

In PdfiumPrinter.LibraryLoader.NativeLibraryLoader.LoadNativeLibrary look for where it checks for !File.Exists(path). Replace that block with this...

if (!File.Exists(path))
{
	var libFound = Directory.EnumerateFiles(assemblySearchPath, fileName, SearchOption.TopDirectoryOnly).SingleOrDefault();
	if (!string.IsNullOrEmpty(libFound))
		path = libFound;
	else
		throw new FileNotFoundException($"Native Library not found in path {path} or {Path.Combine(assemblySearchPath, fileName)}. " +
			$"Verify you have included the native Pdfium library in your application, " +
			$"or install the default libraries with the bblanchon.PDFium NuGet.");
}

Alternatively, and I don't see this documented anywhere, it appears that maybe you could also call the static PdfiumPrinter.PdfLibrary.EnsureLoaded(pathToNativePDFiumDLL); to preset it explicitly to the location of your choice. This should work, but doesn't automatically adjust to different build types.

I hope this is helpful to someone else.