You use IIS because you want to use ASP. You can't replace ASP with Nginx, it's an entire development stack, not just a webserver. And I actually like ASP. It's

You use IIS because you want to use ASP. You can't replace ASP with Nginx, it's an entire development stack, not just a webserver. And I actually like ASP. It's fast, easy to develop with, easy to deploy and there's great library support.