几个C＃项目如何在没有繁琐的手动复制的情况下使用非托管DLL？

Question

We wrote an unmanaged DLL with a simple C-style API last month. It works and all is fine with it.

Today, we're writing a demo app using this DLL. This is part of a whole new Solution in Visual Studio 2013. It compiles and runs fine, until it tries to use the DLL's API, where we get DllNotFoundException.

Same thing happened last week with a test console app. The cheap-quick workaround was to copy the DLL from the workspace it was made in, and plop a copy into bin/x64/Debug/ in the project's folder in the new workspace. The problem went away.

Sure, we could do the same today for the new demo app, and get on with life, but this seems goofy. We have several test and demo apps, and apps to be given to customers, numbering fifteen or so. Surely we are not supposed to manually copy the DLL, after every change to it, into fifteen different bin/x64/Debug/ for fifteen different projects. And more, since we'll have Release versions too.

Despite reading many blogs, articles, MSDN pages about unmanaged DLLs and Solutions and Projects and right-click to "Add References..." and all that, I've not seen any clear explanation how one should deal with multiple projects using one DLL. Seems like there should be some way we could copy the DLL to one place, and tell all the projects just once to go look there.

Relevant Side Question: We've tried the "Add References..." things, but it didn't like our DLL. Is this not applicable to unmanaged DLLs written in C? We don't see a clear statement whether or not we should be using Add Reference.

Answer 1

For your program to run it needs all its dependencies to be available, so the dll has to be included in the set of files you ship. For managed assemblies the build process copies these files automatically, but for unmanaged dlls you need to tell the build system what to do.

The usual way is to either

• edit the post-build step (in your app's project properties) and add a copy/xcopy/robocppy command that copies the file to the output folder. You can embed macros in the filenames to locate the folders so that the project remains relocatable.

• add the file to the project and get its properties in the solution explorer. Then set it to be "copied if newer".

By doing this the latest version of the dll is copied every time you do a build, and you can forget about it.