Brad Brad - 29 days ago 8
C# Question

C# namespace alias - what's the point?

I have been trying to learn more about the C# language, but I haven't been able to see a situation where one would use namespace aliasing like

using someOtherName = System.Timers.Timer;


It seems to me that it would just add more confusion to understanding the language.
Could some one please explain.

Thanks

Answer

That is a type alias, not a namespace alias; it is useful to disambiguate - for example, against:

using WinformTimer = System.Windows.Forms.Timer;
using ThreadingTimer = System.Threading.Timer;

(ps: thanks for the choice of Timer ;-p)

Otherwise, if you use both System.Windows.Forms.Timer and System.Timers.Timer in the same file you'd have to keep giving the full names (since Timer could be confusing).

It also plays a part with extern aliases for using types with the same fully-qualified type name from different assemblies - rare, but useful to be supported.


Actually, I can see another use: when you want quick access to a type, but don't want to use a regular using because you can't import some conflicting extension methods... a bit convoluted, but... here's an example...

namespace RealCode {
    //using Foo; // can't use this - it breaks DoSomething
    using Handy = Foo.Handy;
    using Bar;
    static class Program {
        static void Main() {
            Handy h = new Handy(); // prove available
            string test = "abc";            
            test.DoSomething(); // prove available
        }
    }
}
namespace Foo {
    static class TypeOne {
        public static void DoSomething(this string value) { }
    }
    class Handy {}
}
namespace Bar {
    static class TypeTwo {
        public static void DoSomething(this string value) { }
    }
}