How to call a function on the client from the server side?

Question

C++ / C#

Can the server call a function on the client, so that the called function is executed on the client and the value is returned to the server?
For the client to execute a function without knowing its body. For safety.

Answer 1

For the client to execute a function without knowing its body

This is impossible, the client will execute the code, you can obfuscate it, compile it, or somehow complicate its receipt, but the code will still be visible to the client.

Answer 2

Yes, it's possible.
The topic that interests you is discussed under the term "means of protecting the program from hacking."
Or "mounted means of protecting the program from hacking"
There are many interesting technologies.

Answer 3

Read about Roslyn, for example here Albahari, Joseph, Albahari, Ben.
A45 C# 6.0. Directory. Complete Description of the Language, 6th ed. : Per. from English. - M. : LLC
"ID Viljame", 2016. - 1040 p.: ill. - Paral. tit. English
ISBN 978-5-8459-2087-4 (rus.)
In the last chapters it is well described, you can compile and execute a string, without any traces in the system.