question about using directive

daniel mark

Hello all:

I read the following statement from MSDN

http://msdn2.microsoft.com/en-us/library/sf0df423(vs.71).aspx

A using directive does not give you access to any namespaces that may be nested in the namespace you specify.

What is the real meaning behind this statement

I tested the following code and it works !

Thank you

-Daniel

Code Snippet

// cs_using_directive.cs

using MyCompany.Proj.Nested;

namespace MyCompany.Proj
{

public class MyClass
{

public static void DoNothing()
{
}
}

namespace Nested // a nested namespace
{
public class ClassInNestedNameSpace
{
public static void SayHello()
{
System.Console.WriteLine("Hello");
}
}
}
}

public class UnNestedClass
{
public static void Main()
{
ClassInNestedNameSpace.SayHello(); // access function through using directive
}
}

Mattias Sjogren

I believe they simply mean that if you specify

usign System;

that will not give you access to types in sub-namespaces like System.Data.

bmains

Hey,

It means that if you specify using System.Collections, it does not automatically give you access to all the classes in using System.Collections.Generic; rather, you have to specify both if you need to access both.

Brian

michhes

...just to add to this... Namespaces don't offer any form of visibility modifiers. Your example works because your namespace declarations are equivalent to this:

Code Snippet

namespace MyCompany.Proj
{

public class MyClass { ... }

}

namespace MyCompany.Proj.Nested
{
public class ClassInNestedNameSpace { ... }
}

James Curran

Ok, let us assume that you "MyCompany.Proj" is, as defined in you message, but instead of

using MyCompany.Proj.Nested;

we wrote just

using MyCompany.Proj;

Then we could write

MyClass myc = new MyClass();

because the "using" gave us access to the namespace.

However we could not write:

ClassInNestedNameSpace cinns = new ClassInNestedNameSpace();

nor could we write:

Nested.ClassInNestedNameSpace cinns = new Nested.ClassInNestedNameSpace();

because the "using" does not give us access to the nested namespace, only the specified namespace.

We would have to write either:

using MyCompany.Proj.Nested;

ClassInNestedNameSpace cinns = new ClassInNestedNameSpace();

or

MyCompany.Proj.Nested.ClassInNestedNameSpace cinns = new MyCompany.Proj.Nested.ClassInNestedNameSpace();