Simple Singleton pattern implementation using System.Lazy<T>. The extending class needs to implement a private parameterless constructor to complete the pattern. Generic type parameter passed to Singleton should be the extending class type.

C#: Singleton

using System;
 
public abstract class Singleton<T> where T : class
{
 private static readonly Lazy<T> _instance = new Lazy<T>(() => CreateInstance());

 public static T Instance { get { return _instance.Value; } }

 private static T CreateInstance()
 {
   return Activator.CreateInstance(typeof(T), true) as T;
 }
}