How get the default namespace of project csproj (VS 2008)

There is actually a (subtle) difference between the two. Imagine you have the following code in File1.cs:

// File1.cs
using System;
namespace Outer.Inner
{
    class Foo
    {
        static void Bar()
        {
            double d = Math.PI;
        }
    }
}

Now imagine that someone adds another file (File2.cs) to the project that looks like this:

// File2.cs
namespace Outer
{
    class Math
    {
    }
}

The compiler searches Outer before looking at those using directives outside the namespace, so it finds Outer.Math instead of System.Math. Unfortunately (or perhaps fortunately?), Outer.Math has no PI member, so File1 is now broken.

This changes if you put the using inside your namespace declaration, as follows:

// File1b.cs
namespace Outer.Inner
{
    using System;
    class Foo
    {
        static void Bar()
        {
            double d = Math.PI;
        }
    }
}

Now the compiler searches System before searching Outer, finds System.Math, and all is well.

Some would argue that Math might be a bad name for a user-defined class, since there's already one in System; the point here is just that there is a difference, and it affects the maintainability of your code.

It's also interesting to note what happens if Foo is in namespace Outer, rather than Outer.Inner. In that case, adding Outer.Math in File2 breaks File1 regardless of where the using goes. This implies that the compiler searches the innermost enclosing namespace before it looks at any using directive.

• None: The file is not included in the project output group and is not compiled in the build process. An example is a text file that contains documentation, such as a Readme file.

• Compile: The file is compiled into the build output. This setting is used for code files.

• Content: Allows you to retrieve a file (in the same directory as the assembly) as a stream via Application.GetContentStream(URI). For this method to work, it needs a AssemblyAssociatedContentFile custom attribute which Visual Studio graciously adds when you mark a file as "Content"

• Embedded resource: Embeds the file in an exclusive assembly manifest resource.

• Resource (WPF only): Embeds the file in a shared (by all files in the assembly with similar setting) assembly manifest resource named AppName.g.resources.

• Page (WPF only): Used to compile a xaml file into baml. The baml is then embedded with the same technique as Resource (i.e. available as `AppName.g.resources)

• ApplicationDefinition (WPF only): Mark the XAML/class file that defines your application. You specify the code-behind with the x:Class="Namespace.ClassName" and set the startup form/page with StartupUri="Window1.xaml"

• SplashScreen (WPF only): An image that is marked as SplashScreen is shown automatically when an WPF application loads, and then fades

• DesignData: Compiles XAML viewmodels so that usercontrols can be previewed with sample data in Visual Studio (uses mock types)

• DesignDataWithDesignTimeCreatableTypes: Compiles XAML viewmodels so that usercontrols can be previewed with sample data in Visual Studio (uses actual types)

• EntityDeploy: (Entity Framework): used to deploy the Entity Framework artifacts

• CodeAnalysisDictionary: An XML file containing custom word dictionary for spelling rules