What namespace will a class have if no namespace is defined

In C#, if I create a class with no namespace, what namespace will I use when trying to instantiate the class?

For example, assume main is...

namespace NamespaceTests
{
	class Program
	{
		static void Main(string[] args)
		{

		}
	}
}

... and assume my namespace-less class is ...

public class test
{
	public string SayHello()
	{
		return "Hello World!";
	}
}

... and assume I have another class by the same name, but having the default namespace...

namespace NamespaceTests
{
	public class test
	{
		public string SayHello()
		{
			return "Hello Moon...";
		}
	}
}

... how would I modify main to include an instance of the namespace-less class and call 'SayHello' to retrieve the message "Hello World!"? Specifically, how would I fully qualify the namespace-less instance of class 'test', especially considering I may have another class also called 'test' but having a namespace, so I need to distinguish...

It's in the global namespace and can be referenced like this:

var x = new global::test();

Types not defined within a namespace will be in the global namespace.

> The global contextual keyword, when it comes before the :: operator, refers to the global namespace, which is the default namespace for any C# program and is otherwise unnamed. > > The following example shows how to use the global contextual keyword > to specify that the class TestApp is defined in the global namespace:

C# class TestClass : global::TestApp { }

In the addition to above answers, it is important to note, what all Type, regardless of its declaration location, has a "fully qualified name", which begins from "global::"

From "O'Relly. C# in a Nutshell":

All type names are converted to fully qualified names at compile time. Intermediate Language (IL) code contains no unqualified or partially qualified names