How to load the code of one script into another?

Question

C++ / C#

How to load the code of one script into another?
For example, PHP has include();
In Java - import
A in C#;

Answer 1

using

Answer 2

What does "upload" mean? If you want to use the methods of class A in class B, plus some additions or modifications, then inherit class B from class A.
If you just want to call the public method of class A in class B, then either class B must have a reference to an instance of the class Or the called method must be static.