Singleton. Lazy реализация.

using System;
using System.Threading;
using System.Linq;

class Program
{
   static void Main(string[] args)
   {
    Console.WriteLine("Main: {0}", DateTime.Now.TimeOfDay);
    Console.WriteLine("Singleton: {0}", Singleton.text);

    Singleton singleton = Singleton.GetInstance();
    Console.WriteLine("Date: {0}", singleton.Date);

    Console.ReadLine();
   }
}

class Singleton
{
    public static string text = "Hello";

    public string Date{get; private set;}

    private Singleton()
    {
        Console.WriteLine("Singleton ctor: {0}", DateTime.Now.TimeOfDay);
        this.Date = DateTime.Now.TimeOfDay.ToString();
    }

    public static Singleton GetInstance()
    {
        Console.WriteLine("Get instance: {0}", DateTime.Now.TimeOfDay);
        return Nested.instance;
    }

    private class Nested
    {
        static Nested(){}
        internal static readonly Singleton instance = new Singleton();
    }
}