How to get the namespace alias operator :: to work under C#?

Question

I've come up against the unlikely scenario when I reference two external assemblies that both have the same namespace and type names. When I try to use the type, the compiler throws an error that it cannot resolve which one I want to use.

I see that C# offers a mechanism to use aliases for references. You can even specify these aliases via the Property window of a reference in Visual Studio 2008. How do I use this alias in my code? As I understand, I should be using the :: operator, but it fails with the following error:

CS0432 - Alias not found

The usual . operator fails as well.

In the output window I see that the compiler gets the alias passed correctly in its command line.

Any pointers on what I may be able to try next are greatly appreciated.

Answer 1

extern alias alias1;
using alias1::Namespace;

HTH, Kent

Answer 2

Try this:

extern alias asm1;
extern alias asm2;

namespace Client
{
    class Program
    {
        static void Main(string[] args)
        {
            asm1.MyNs.MyClass mc1 = null;
            asm2.MyNs.MyClass mc2 = null;
        }
    }
}

And add global,asm1 to the project reference for assembly1 and global,asm2 for assembly2

Answer 3

I think you need to use an extern alias. Anson Horton has a good blog on this problem and how to use extern alias to fix it.

Answer 4

When you reference some assembly in project it has default alias "global". When you add another alias for that assembly, e.g. "global, AssemblyA", you will reference it like this:

using SomeTypeAlias = AssemblyA::Company.Product.SomeType;

or:

void SomeMethod(AssemblyA::Company.Product.SomeType someType) { ... }