Getting Microsoft .NET Framework error on opening PDF files

Win 11 Pro x64, 24H2 (26100.8654). Opening PDF files, I'm getting the error box shown in the screenshot below, and have added a pdf of full message. The error doesn't stop me from seeing the file, and I can usually open others after that w/o problem, but I'm wondering how to fix this. I ran the .NET Framework repair program, but it found too many errors and was sending the results to MS. I've thought about uninstalling/reinstalling Microsoft .NET Framework, but don't find an installed file of that name, only Microsoft ASP.NET Core 8.0.20 - Shared Framework. Please advise.

Maybe corrupt files so try running sfc /scannow in a Powershell or Command window in Administrator mode. Then restart your device.

Above screened issue is not caused by .Net (or Windows) - but whatever PDF viewer (or Plugin) you're using. Try changing the default PDF app to Edge, Firefox or a 3rd party PDF viewer - like Sumatra PDF: Free PDF Reader - Sumatra PDF

This is not so straight foward. I use PDFXChange Viewer (free) for its simplicity relative to 99% of my needs. It was superseded some years ago, and not often updated anymore, by its much more feature ridden and visually busy Editor version. Now, *none* of this .NET Framework error occurred until after I installed the free version of PDFSam Basic and Enhanced7, which had worked fine in Windows 10 (Viewer was still the default for PDFs). With Sam merely present on the computer, when I opened a pdf in Viewer, Sam would throw up a Critical Error popup, but with no information, a behavior I’d never seen any program do before. I uninstalled Sam and the problem disappeared, i.e. no errors of any kind. However, in further testing with Sam’s developers, one of my Sam uninstalls was incomplete; i.e., there were still Critical Error popups although neither Revo Pro nor Programs (CP) showed Sam as still installed. So I went through the registry and a file manager and deleted all mentions of Sam, except a few that couldn’t be. It was after that the .NET Framework error became constant with Viewer on first pdf file opening (after the error, subsequent pdfs open cleanly).

To be clear, this is about free standing pdf files and pdf programs, not within browsers.

neves said:

Above screened issue is not caused by .Net (or Windows) - but whatever PDF viewer (or Plugin) you're using. Try changing the default PDF app to Edge, Firefox or a 3rd party PDF viewer - like Sumatra PDF: Free PDF Reader - Sumatra PDF

Click to expand...

Sumatra is too limited: no typewriter function. PDF24 has the same .NET Framework issue.

wiganken said:

Maybe corrupt files so try running sfc /scannow in a Powershell or Command window in Administrator mode. Then restart your device.

Click to expand...

There were some, but not related to this. There is no .NET Framework error using, e.g., PDFXChange Editor.

highstream said:

Sumatra is too limited: no typewriter function. PDF24 has the same .NET Framework issue.

Click to expand...

True, it's mainly (and was always) - a very lightweight PDF viewer (from back in the days - when Adobe took over a minute to load). But Firefox can compete even with Paid PDF Editors - despite mainly adding this PDF feature while aiming to compete with Microsoft Edge - and beat it in terms of functions, again - it's a web browser - but competes with paid PDF editors.

I’ll check it out. I normally use Opera, so haven’t paid much attention to FF’s capabilities. There’s also PDFXChange Editor, which is not causing the error. I’m also wondering if the next Framework version will solve the problem, since it didn’t occur until I had to deal with Sam.

Working with my Win 11 Pro laptop, PDFXChange Viewer does not throw up .NET Framework errors opening the same files. Got to be something more to it. Perhaps .NET Framework got messed up a bit when I deleted PDFSam entries from the registry.