The specified procedure could not be found. (Exception from HRESULT: 0x8007007F)

My C++ DLL (called from C# application) works fine with Debug version (main C# app in Debug ) but release version(main C# app in Release) gives The specified procedure could not be found. (Exception from HRESULT: 0x8007007F)] System.DllNotFoundException: Unable to load DLL 'D:\TestBluRay.dll': The specified procedure could not be found. (Exception from HRESULT: 0x8007007F) error. I've verified all project settings and those appear to be same for both debug and release. Any idea why this fails for release version only?

Validate that the .DLL is present, and fully up-to-date between both \bin\debug (which works), and \bin\release (which is failing).

Most likely, the .DLL needs either recompiling, or simply copying in if it's a 3rd-party library.

EDIT: Your error indicates that the file may be missing entirely (DllNotFoundException), or that you're referencing a path/directory, instead of a fully qualified path name. "\Drivers\Blu_ray.." isn't a fully-qualified path name, where "C:\Windows\System32\Drivers\Blu_ray.." etc., would be a fully qualified path name.

My guess is that \bin\release\ doesn't have \drivers\blu_ray, whereas \bin\debug\ probably does have \drivers\blu_ray...