call functions

[xyz.net]

Hi everyone
my English and programming levels are low, I hope you still want to answer and help me.
i use c# asp.net .
what i would like to know is if the beautiful solutions i see on this site can call functions in c#
for example, the button that I find at the link

https://www.w3schools.com/howto/howto_js_dropdown.asp

can call the function "function()" ? and how?
Thank you?