.dll reference loads properly into c# project in Debug mode but can't find namespaces in Release

Question

I'm setting up a CI server for my company and integrating Unit Testing. I've chosen to use TeamCity and NUnit, as they've worked well for other organizations I've worked for in the past.

I have TeamCity up and running and I've created just a test Unit Test project for now so I can verify that TeamCity is handling my NUnit configuration properly. In my project, I've added a reference to nunit.framework.dll which lives in a folder at the root of my solution. When I committed up the solution to test, this was the output I got from my build step in TeamCity:

[10:45:35][Csc] UnitTesting.cs(5, 7): error CS0246: The type or namespace name 'NUnit' could not be found (are you missing a using directive or an assembly reference?)

[10:45:35][Csc] UnitTesting.cs(16, 10): error CS0246: The type or namespace name 'Test' could not be found (are you missing a using directive or an assembly reference?)

[10:45:35][Csc] UnitTesting.cs(16, 10): error CS0246: The type or namespace name 'TestAttribute' could not be found (are you missing a using directive or an assembly reference?)

[10:45:35][Csc] UnitTesting.cs(13, 6): error CS0246: The type or namespace name 'TestFixture' could not be found (are you missing a using directive or an assembly reference?)

[10:45:35][Csc] UnitTesting.cs(13, 6): error CS0246: The type or namespace name 'TestFixtureAttribute' could not be found (are you missing a using directive or an assembly reference?)

When I went back to my IDE, I was able to build the solution without seeing those error messages. Until I switched to Release config. As soon as I switched the config and built the solution, I got the same messages in my IDE that I got from TeamCity.

I tried adding the .dll file to my project again, but Visual Studio complained that the reference is already there and prevented me from adding it again.

What gives?

Answer 1

Pretty much what happened here is: Visual Studio forgot what was going on and lost touch with reality for no reason and didn't know where to look for the .dll. I don't know why it only happened in Release config, but I deleted the reference and re-added it and all is well and good.