What's the difference in these ways of creating the static instance for a singleton?

Question

I have had a bug recently that only manifested itself when the library was built as a release build rather than a debug build. The library is a .NET dll with a COM wrapper and

Answer 1

Just reiterating what Marc Gravell said, but it sounds a lot like a beforefieldinit problem, which means the empty static constructor is your solution. You'd need to post any and all constructors in the class to get a definitive answer.

The second method has the advantage of lazy loading (where that is an advantage).

Answer 2

Try adding an (empty) static constructor, or initialize the singleton in a static constructor.

Jon Skeet has a full discussion of singleton patterns here. I'm not sure why it failed, but at a guess it could relate to the "beforefieldinit" flag. See his 4th example, where he adds a static constructor to tweak this flag. I don't claim to be an expert on beforefieldinit, but this symptom seems to fit some of the symptoms discussed here.