When refactoring any code, R# ignores code that may be #ifdef'd out. Many people have extra code like #if DEBUG #else ... #endif. The problem is that when refactoring code, R# only changes code that meets the current build symbols. The next time someone builds using a different set of build defines, then the build will break as code meeting that criteria wasn't refactored along with the other code. R# needs to include all code (including that "#if'd out") when doing any sort of analysis and refactoring (find usages, rename, etc).