Visual Studio中的命名空间在哪里

Question

I am new to Visual Studio and C#. I went through the tutorials on C# and all the sample programs I went through, were written inside namespaces. But when I used a template on Visual Studio, all the predefined codes weren't inside namespaces. Shouldn't the classes in the programs be in namespaces? Why aren't they present by default? Should I define them?

Thanks!

[edit] Below is the code in one of the files that doesn't have a namespace.

using System;   
using System.Web.Security;  

public partial class Login : System.Web.UI.Page  
{   
    protected void btnSubmit_Click( object sender, EventArgs e )  
    {  
        // Note: Add code to validate user name, password. This code is for illustrative purpose only.  
        // Do not use it in production environment.          
        FormsAuthentication.RedirectFromLoginPage( txtUserName.Text, false );  
    }  
}

Answer 1

There is a default namespace declared in your Project's properties. But it's a good practice to declare it explicitly. If your project has no folders, all classes are inside the same namespace so it is redundant.

Answer 2

A namespace is designed for providing a way to keep one set of names separate from another. The class names declared in one namespace does not conflict with the same class names declared in another. Please refer https://msdn.microsoft.com/en-us/library/z2kcy19k.aspx for more details.

Answer 3

General

Namespaces are basically just a way to group your classes and give your Project a structure.

Classnames must be unique for each namespace.

You can also sort of "encapsulate" your Namespaces. For Example you can create some Namespaces SomeProject , SomeProject.Core and SomeProject.UI

If you wite using SomeProject. the Intellisense would now suggest Core and UI .

Usasge

So to use a Class MyClass from SomeProject.Core you would have three possibilities to use it.

1. using Direcitve

using SomeProject.Core;

calling it with MyClass

2. Calling it with the entire Namespace

SomeProject.Core.MyClass

3. Explicite using Directive (rarely used, but maybe useful for longe namespaces)

using AnyName = SomeProject.Core;

call MyClass with AnyName.MyClass

So i guess thats it for the moment.. if i forgot anything just tell me in the comments