c#中命名空间的幕后花絮？

Question

using System;

namespace HelloWorld
{
    partial class Program
    {
          static void Main(string[] args)
        {
            Console.WriteLine();
        }
    }
} 

my question is when we use using System at the top,are all the codes in that namespace loaded behind the scene in this namespace(HelloWorld)???

Answer 1

using does not change how code is loaded. It only changes which namespaces are allowed to be implicitly assumed when the compiler parses and compiles the code. I think the generated output from the compiler is the same as if you don't use using , but instead explicitly write it the full name of every reference.

But to answer your other question, yes, every object in the namespace is affected, so you should be able to refer to Console without explicitly including System. before it. Keep in mind that using is different than adding a reference. If you don't have a reference to System.dll, you'll still get an error.

Answer 2

Namespaces does nothing to the compiled program, it is just a way for you to organize your code. Nothing is loaded behind the scene. When two classes are in the same namespace, you dont need to add a using to be able to reference that class.

Ofcourse, if the namespace you are using is located in an assembly that isn't automatially referenced you will have to add a reference also. 'using' does not do that for you.

Here's a good reference for namespaces:

https://www.programiz.com/csharp-programming/namespaces