Simple Singleton Pattern in C#

    sealed class Singleton
    {
        private static readonly Singleton m_Instance = new Singleton();
 
        // Prevent instance creation from other classes
        private Singleton() {
            throw new Exception();
        }
 
        public static Singleton Instance { get { return m_Instance; } }
 
        // Non-static instance members here...
    }

    internal sealed class Singleton
    {
        private static readonly object SyncRoot = new object();
        private static volatile Singleton m_Instance;
        // Prevent instance creation from other classes
        private Singleton()
        {
            throw new Exception();
        }
 
        public static Singleton Instance
        {
            get
            {
                if (m_Instance == null)
                {
                    lock (SyncRoot)
                    {
                        if (m_Instance == null)
                        {
                            m_Instance = new Singleton();
                        }
                    }
                }
                return m_Instance;
            }
        }
 
        // Non-static instance members here...
    }

Quote:

An exception thrown inside Singletin's .ctor will be thrown on type initialization (instead of first access to Instance property and even if you will never use it)