Namespace-less types

Daily Knowledge Drop

Types in C# do not have to belong to a specific namespace - it is just standard convention that they do, however this is not a requirement. The global alias, along with the namespace alias qualifier :: can be used to reference types without a namespace in the event of a naming conflict.

Usage

Consider the following basic example - a simple wrapper class, belonging to a namespace, which will output a string to the console:

namespace GlobalKeyword;

public class ConsoleWrapper
{
    public static void OutputToConsole(string output)
    {
        Console.WriteLine(output);
    }
}

The usage is straight forward:

namespace GlobalKeyword;

public class Program
{
    public static void Main()
    {
        ConsoleWrapper.OutputToConsole(
            $"Written to console by instance of '{nameof(ConsoleWrapper)}'");
    }
}

Suppose we reference a Nuget package in our project - it just so happens the require functionality is contained in the package, in a class also called ConsoleWrapper, however, it doesn't contain a namespace:

public  class ConsoleWrapper
{
    public static void Output(string output)
    {
        Console.WriteLine(output);
    }
}

If we try reference the new class in our Main method:

namespace GlobalKeyword;

public static void Main()
{
    // old class in same namespace as Main
    ConsoleWrapper.OutputToConsole(
        $"Written to console by instance of '{nameof(ConsoleWrapper)}'");

    // new class without a namespace
    ConsoleWrapper.Output(
        $"Written to console by instance of '{nameof(GlobalKeyword.ConsoleWrapper)}'");
    
}

Then the following compile-time error occurs:

'ConsoleWrapper' does not contain a definition for 'Output'

As the newly introduced ConsoleWrapper has no namespace, we cannot fully qualify it to resolve the conflict. However, as it has no namespace, it gets put into the global namespace which can be referenced using global:::

namespace GlobalKeyword;

public static void Main()
{
    // old class in same namespace as Main
    ConsoleWrapper.OutputToConsole(
        $"Written to console by instance of '{nameof(ConsoleWrapper)}'");

    // new class in no/global namespace
    global::ConsoleWrapper.Output(
        $"Written to console by instance of '{nameof(GlobalKeyword.ConsoleWrapper)}'");
    
}

Problem solved!

Notes

This is a very rare issue to encounter, as it requires two unlikely scenarios to occur:

• A type to not have a namespace
• The type without a namespace to have the same name as another type (either user defined, or reference)

The vast majority of types do have namespaces, so the chances of encountering this issue are small - however, if it is encountered, the global alias can be used to resolve the conflict.

References

:: operator (C# reference)

Daily Drop 148: 29-08-2022

At the start of 2022 I set myself the goal of learning one new coding related piece of knowledge a day.
It could be anything - some.NET / C# functionality I wasn't aware of, a design practice, a cool new coding technique, or just something I find interesting. It could be something I knew at one point but had forgotten, or something completely new, which I may or may never actually use.

The Daily Drop is a record of these pieces of knowledge - writing about and summarizing them helps re-enforce the information for myself, as well as potentially helps others learn something new as well.