Don't confuse using with includes. Using in C# is nothing but a shortcut and has no impact on performance.

Example:
PHP Code: 
System.Console.WriteLine("You know...");
System.Console.WriteLine("Writing system all the time gets anoying real quick.");
System.Console.WriteLine("That's why 'using' is the best thing since sliced bread!"); 
Why should we write the System namespace all the time to access the Console class? We don't. So we add:
PHP Code: 
using System
So we can just:
PHP Code: 
Console.WriteLine("You know...");
Console.WriteLine("Writing system all the time gets anoying real quick.");
Console.WriteLine("That's why 'using' is the best thing since sliced bread!"); 
We can also create an alias:
PHP Code: 
using System;
using c System.Console
To do:
PHP Code: 
c.WriteLine("You know...");
c.WriteLine("Writing system all the time gets anoying real quick.");
c.WriteLine("That's why 'using' is the best thing since sliced bread!"); 
The closest you'll get to include()/require() in a language like C# is adding references to other assemblies in Visual Studio (well you can load them at runtime or even compile and run source code at runtime but that's on a whole other level, lol).
Hyperz Reviewed by Hyperz on . [c#] variables, ifs, simple math and drawing objects Here is a little tutorial explains how to declare and use strings and integers, how to perform a basic integrity check and how to make use of these values by using an object. It also shows how to create these objects without using the Design view of Visual Studio. The code has been commented to make it easier to read, and is fully functional. You can simply copy-paste its entirety into a new project. using System; using System.Collections.Generic; using System.ComponentModel; using Rating: 5