Strange issue with DLL reference

Ok, here is one that my limited mind cannot figure out:

We have an existing .Net app that uses a .dll that creates PDF files from a vendor. A setting in an older version would underline a group of words, but 1) did not underline the spaces between the words, and 2) put the underline at the next pixel below the letters, so there was no white space between the letters and the underline. This is the version of the .dll we started with.

Company X puts out a new version of the .dll that underlines the spaces between words, and drops the underline down a couple of pixels.

We uninstall the old version of the .dll, remove it from the GAC, making sure that there are no copies of the .dll anywhere on the system, and the install the new version. In VS, under references, we can see that the .dll is the latest version. However, when we run the app, the result is that the words are underlined, and the underline is down a couple of pixels, but the spaces between the words are not underlined.

We created a new test project, referenced the .dll, and got the desired results, with spaces underlined, and the underline down a couple of pixels.

Sooooo...the existing project, that used to reference the old version, but now references the ne开发者_如何学编程w version, is showing behavior that is a combination of the old and new versions. How is this possible? Is there something buried in the inner working of a VS project that could cause this? Has anyone ever seen anything like this?

Thanks in advance for any ideas

Update I have it working correctly in the IDE, but when it gets installed on a machine, it is still showing the hybrid results. There must be something in the setup project that is not pulling the .dll correctly in.

If you have a Class Library Project (e. g. MyProject.Core) and you have inside that Project a reference to an update of a DLL (e. g. ThirdParty.dll), if you want that the IntelliSense of the Visual Studio updates the changes of that new DLL, try this:

1. Double click in the References folder of your MyProject.Core project
2. Delete the ThirdParty.dll old reference
3. Add the ThirdParty.dll new reference
4. Rebuild MyProject.Core
5. Check that VS IntelliSense has been updated