User753101303 posted
Hi,
Technically speaking only the browser can open a new browser window. C# code running on the server side doesn't know at all about browser windows and is just responding to http requests.
You can still render JavaScript code from C# that will then run in the browser or if you need to run an http query without really opening a window, you can handle one of those two http querires from the server side using for example the HttpClient class.
Make sure to understand what haqppens on the client side and what happens on the web server side.