Tuesday, July 17, 2007

Shared Assemblies, Components, and Applications

Here's the situation:
You have a shared assembly which contains a lot of useful utilities called SharedAssembly.dll

You create a customized component that uses SharedAssembly.dll called ComponentA.dll

You create a full application which uses SharedAssembly.dll and ComponentA.dll called App1.exe

In VS2005 you setup your solution to include all the projects: App1, ComponentA, and SharedAssembly. You setup the references as Project references. Now, when you build the solution, VS figures out it needs to build SharedAssembly first, then ComponentA, then App1. The end result is App1 and ComponentA both use the same version of SharedAssembly. This is wonderful.

But what if you wanted to change it so that ComponentA wasn't included as a project in the solution file? Instead you want to release ComponentA as dll files that can simply be referenced by App1. The problem is that you now have two different versions of SharedAssembly.dll. If you set it up this way you'll get a runtime error because the framework detects that the version of SharedAssembly.dll is not what was expected by ComponentA.dll. Is there any way to get a setup like this working?

I want ComponentA to be like its own little mini-application, with its own versions of dlls, completely independent from App1.

My mind is immediately drawn to Java's jar files, but I don't really know how they work.

I've tried a little utility from MS Research called ILMerge which takes a set of dlls and combines them into a single dll. However, this didn't work. An exception was thrown at run time when the second SharedAssembly namespace was encountered.

I also tried installing the dlls in the GAC. However, it turns out you can't reference a dll in the GAC from Visual Studio: "This is because the GAC does not have full support for all design-time pieces of an assembly -- while you have access to the DLL itself, you will not have access to PDB symbols nor XML documentation files." (link)

Any ideas?

1 comment:

  1. Hi Kevin

    I have a suggested solution for this problem, See if it helps you.

    Please let me know what do you think.

    Yonatan Leonov