A free and open-source web framework that enables developers to create web apps using C# and HTML, developed by Microsoft.
you would use jsinterop to have js test if the files were loaded, and if not use javascript to load the script and css file.
load js file:
https://www.educative.io/answers/how-to-dynamically-load-a-js-file-in-javascript
load css file:
https://www.geeksforgeeks.org/how-to-load-css-files-using-javascript/