The singleton pattern is used in almost all modern day programming languages, so why do I keep finding it written incorrectly in so many applications, so lets start with the right way

public sealed class SimpleNoLockLazy
    {
        static readonly SimpleNoLockLazy instance = new SimpleNoLockLazy();

        // Explicit static constructor to tell C# compiler
        // not to mark type as beforefieldinit
        static SimpleNoLockLazy()
        {
        }

        SimpleNoLockLazy()
        {
        }

        public static SimpleNoLockLazy Instance
        {
            get
            {
                return instance;
            }
        }
    }

So why this implementation?   The reason for using a Singleton is for performance in a multi-threaded environment and this pattern is not only simple, but it is the fastest.  I have attached a benchmark application, which is based on Jon Skeet’s benchmark, but testing using a Parallel processes.

Benchmark.zip (9.98 kb)

I found Jon Skeet’s article very useful