If you want to get a feel for the singleton pattern in C# one of the best resources I always revisit is on John Skeet’s (@jonskeet) website http://www.yoda.arachsys.com/csharp/singleton.html
I encourage you to read the above article to appreciate the little intricacies or requiring static constructor, BeforeFieldInit, volatile etc.
However: If you just want the easiest lazy evaluation solution in .net4+, then you’ve come to the right place.
Lazy<T> guarantees thread-safe lazy construction.
If I’d followed Jon’s notice, at the top of the page I linked to, I would have seen the post is now located here and moreover, he covers the Lazy<T> approach there.