CODEWITHSUNDEEP
c#namespacesclass
pgb
pgb

Reputation: 25011

Class with same name in two assemblies (intentionally)

I'm in the process of migrating a library that is written in C++ and has a C# wrapper. The C# wrapper (LibWrapper) has a set of classes with namespaces, like:

namespace MyNamespace
   class MyClass
   class MyOtherClass

My new library, LibraryCS contains the same namespaces and class names as LibWrapper (per user requirement), so I also have:

namespace MyNamespace
   class MyClass
   class MyOtherClass

Now that the migration is done, I'm in the process of creating a test that compares the results of using both libraries, to validate the migration. However, when I try to reference MyNamespace.MyClass I get a compiler error (expectedly!) that says "MyNamespace.MyClass is defined in both LibWrapper and LibraryCS".

Is there any trick around this issue, that will allow me to use two classes with the exact same name but from different assemblies in the same client code?

Alternatively, is there any other way to test this?

Renaming the migrated namespace to something like MyNamespace2 will of course work, but we were asked not to do it, in order to keep the client code easier to migrate.

Upvotes: 41

Views: 23208

Answers (4)

Quartermeister
Quartermeister

Reputation: 59179

You can use an extern alias to reference types with the same fully qualified name from different assemblies. Select the reference to LibraryCS and update Aliases in the properties page from "global" to "LibraryCS", and add extern alias LibraryCS; to the top of your source file, and then you can use LibraryCS::MyNamespace.MyClass to refer to the class in LibraryCS. You can use MyNamespace.MyClass or global::MyNamespace.MyClass to refer to the class in LibWrapper, or you can use an alias for that reference as well.

Upvotes: 69

Sin
Sin

Reputation: 1864

Saw this question and answer and it helped me. How ever for those who need a detailed explanation on the same, i found a link which is really useful.

Extract from the link.

Using different versions of the same dll in one application

step 1: using the VS IDE. Add the reference to both the dlls in your client application solution. Then in the Solution Explorer under the reference node select the first (old version) class library. In the property window change Aliases field from global to oldVer. lly, newVer for the Newer version.

Step 2: use the below code as the first statements where you plan to reference it

extern alias oldVer;
extern alias newVer;

now to use,

Console.WriteLine(oldVer::MyLibrary.MyClass.method());
Console.WriteLine(newVer::MyLibrary.MyClass.method());

Hope this helps.

Upvotes: 4

Shea
Shea

Reputation: 11243

You could load the first assembly at runtime then use reflection to instantiate it and execute it's method. Then unload that assembly, load the second assembly and use reflection to create it and run its methods.

It'd probably be easier to use 2 separate processes then compare the resulting output...

Upvotes: 0

Reed Copsey
Reed Copsey

Reputation: 564891

In order to load both of these classes in the same executable, you could to load them in a separate Application Domain. This would let you test the assembly, then fully unload it and load the second one and test it.

For details on how to do this, see How to: Load Assemblies into an Application Domain and Unload an Application Domain.

Upvotes: 4

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