C#

public sealed class Singleton
{
  private static Singleton instance;
 
  private Singleton() {}
  // Makes sure that only one instance exists.
  private static Singleton Instance
  {
    get
    {
      // Thread-safe initialization.
      if (instance == null)
        lock (typeof(Singleton))
          if (instance == null)
            instance = new Singleton();
      return instance;
    }
  }
  private void doSomething()
  {
    Console.WriteLine("Something done.");
  }
  public static void DoSomething()
  {
    Instance.doSomething();
  }
}

if (instance == null)
  lock (typeof(Singleton))
    if (instance == null)
      instance = new Singleton();

ldarg.0
ldc.i4.1
stfld Singleton.initialized

public static void DoSomething()  <br />
{    <br />
    Instance.doSomething();  <br />
}

public static void DoSomething()  <br />
{    <br />
    lock (typeof(Singleton))<br />
    Instance.doSomething();  <br />
}

public static int Add(int a, int b)
{
  return a + b;
}

<br />
public sealed class SingletonNoInstance<br />
{<br />
    private static Object m_objInit = new InitObj();<br />
<br />
    private static Object InitObj()<br />
    {<br />
        // do intialization here<br />
        // ...<br />
        return new Object();   <br />
    }<br />
  <br />
    public static void ThreadSafeDoSomething()  <br />
    {    <br />
        lock(typeof(SingletonNoInstance))<br />
        {<br />
            // do something here<br />
            // ...<br />
        }<br />
    }<br />
}<br />

public sealed class Singleton<br />
{<br />
        private Singleton(){}<br />
        public static readonly Singleton Instance = new Singleton();<br />
}