How to use my written compiler to read files on web?

Question

I'm creating a toy language that compiles to javascript.

Now that it's almost done i'm wondering how could I make the server to understand custom files (like 'myfile.mylang') and compile it with the compile i writed (in c#).

for instance, call on a webpage and then, my compiler could be used to transform it to js.

I hope i was clear, thanks in advance for your time