Question

Okay, there’s System and System.Web. Am I correct in that the structure this suggests is:

namespace System
{
    // all of the outer namespace members

    namespace Web
    {
        // all of the inner members
    }
}

And that when a namespace is nested within another, having a using directive with the parent/outer namespace only doesn’t automatically bring in the child/nested namespace? In other words:

using System;

public class Example
{
    public Example()
    {
        context1 = new HttpContext(); // won't work

        context2 = new System.Web.HttpContext(); // will work
    }
}

Just trying to see if I actually understand this correctly.

Answer 1

You could nest namespaces and any using directive would only grant access to the members defined within the specific namespace you are referencing.

So from your example:

namespace System
{
    // all of the outer namespace members

    namespace Web
    {
        // all of the inner members
    }
}

Referencing System would grant you access to the outer namespace members and referencing System.Web would grant you access to all of the inner namespace members.

But this is atypical and usually namespaces are defined only once within a file. The dot-notation typically follows a folder or project structure, so files that were nested as such:

WebApplication
    - Models
        - MyModel.cs
    - Controllers
        - MyController.cs

Might use namespaces of WebApplication.Models and WebApplication.Controllers.

I can’t think of a great example off the top of my head where you would want to nest namespaces, but there may be a good reason to. However, it would be considered an exception to the rule, in my opinion.