The ?BDS? symbol is defined, the code sample is: ----------------- #if DEVENV return _instance ?? (_instance = new DevenvSolutionHelper()); #elif BDS return _instance ?? (_instance = new BdsSolutionHelper()); #else #error There is no IDE selected for support, consider defining one of the symbols on the project. #endif ----------------- Of these three choices, R# displays the second and the third as active (BDS and #else) by color, and highlights the #error tag as an error. C# compiler passes the compilation and from its point of view only the second choice is active. I think that even in the current R# parsign mode for the defines this case should work OK, as it does for the two-choice case.