Can I use a C# codebehind to return my JSON?

Can I use a C# code behind to return my JSON?
I tried and it threw an error, I might be doing something wrong.

I am currently writing my JSON to a text file through CS by and it works great.
However, my columns are dynamic depending upon user preferences, so the text file will keep getting regenerated, my concern is that it might get locked if people try to access the page at the same time.

I need quite a bit of back-end processing which I already have in C#, trying to avoid duplicating everything in PHP.

Thanks,
Meghna