A generic singleton

Taken from: http://andyclymer.blogspot.com/2008/02/true-generic-singleton.html
Changed by Simon Hughes 20th Feb 2008

using System;

using System.Reflection;

// Use like this

/*

public class Highlander : Singleton<Highlander>

{

    private Highlander()

    {

        Console.WriteLine("There can be only one...");

    }

}

*/

public class Singleton<T> where T : class

{

    private static T instance;

    private static object initLock = new object();

    public static T GetInstance()

    {

        if (instance == null)

        {

            CreateInstance();

        }

        return instance;

    }

    private static void CreateInstance()

    {

        lock (initLock)

        {

            if (instance == null)

            {

                Type t = typeof(T);

                // Ensure there are no public constructors...

                ConstructorInfo[] ctors = t.GetConstructors();

                if (ctors.Length > 0)

                {

                    throw new InvalidOperationException(String.Format("{0} has at
                    least one accesible ctor making it impossible to enforce
                    singleton behaviour", t.Name));

                }

                // Create an instance via the private constructor

                instance = (T)Activator.CreateInstance(t, true);

            }

        }

    }

}