Loading C# DLL to C++/CLI - dependencies directory

Question

I wrote a dll c++/cli library which uses my other c# dll library. C++/cli library works fine when I've got c# dll in the same folder as application which calls it. This library will be finally loaded to many applications and a C# dll must not be copied into directory with application. It has to be in the same folder as c++/cli library, but in that cases I've got System.IO.FileNotFoundException. My suggestion is to load c# library manually or to change path where f.ex. firefox is looking for dependencies, but I tried with LoadLibrary() and Assembly::LoadFrom() methods to force loading from right directory. Of course I added directory path with dll to system PATH. I work on VS2010.

Answer 1

You don't change the default directory where an application will look for dlls.

At design time put your dll in some well know location, the one you are going to deploy to. Add a reference to it, make sure it's set to Don't copy ever, otherwise it will end up in the bin folder. You have to do this otherwise it won't compile.

When you deploy, you'll need one package to deploy common dlls, and one for each application. Careful you don't create your own version of dll hell, if appA needs an older or new version of the common dll, compared to AppB

Add an AppDomain.AssemblyResolve event to main (for windows app). At run time the event handler will get fired when you reference a type in your dll, and the assembly has not yet been loaded.

In there you load it from the well known location. That usually in config, or in a relative path.

E.g.
AllMyApps
  CommonDLLS
  MyFirstApp

So the path you load the required common dll from would be "..\\CommonDlls\\MyCommondll.dll".

NB you will want to secure the dlls in some way, otherwise a bad guy might be able to inject their version of one in to your app, which would be bad...

You can use this mechanism to get the dll from a remote server or a database blob as well.

The simplest case is only a few lines of code, just look the event up. Took me about 15 minutes to get this going in a similar scenario.

Not on this machine though, otherwise I'd have pasted in the code.