Why I haven't updated the GA App and its book links in a few years

What happened is that I was putting the books on my onedrive and then creating a link url on the site. The urls had a fixed format, with an id parameter. I store the id with the book record in the books table, and when generating the page HTML, generate the book's onedrive url with the id. A couple years ago, onedrive changed the format of their urls. The old book urls still work, but new urls have a different format. So I need to rewrite the code that generates the url. But I can't. I wrote the GA app four years ago, and Microsoft's changed its web tools (moved from old .NET to new .Net Core -- open source, works on Mac and Linux) and Visual Studio no longer supports the old .NET tools I used four years ago. So I need to upgrade to .NET core to compile any new code and rebuild the website. And I haven't got around to that upgrade project yet. Currently I'm more interested in learning client technologies, pushing more work to the browser, just serving files, and not having to keep a database running in the cloud to support the app.