What is the best way to implement Singleton Design Pattern in C# with performance constraint?

Question

Please let me know what the best way to implement Singleton Design Pattern in C# with performance constraint?

Answer 1

public class Singleton 
{
    static readonly Singleton _instance = new Singleton();

    static Singleton() { }

    private Singleton() { }

    static public Singleton Instance
    {
        get  { return _instance; }
    }
}

Answer 2

Paraphrased from C# in Depth: There are various different ways of implementing the singleton pattern in C#, from Not thread-safe to a fully lazily-loaded, thread-safe, simple and highly performant version.

Best version - using .NET 4's Lazy type:

public sealed class Singleton
{
  private static readonly Lazy<Singleton> lazy =
      new Lazy<Singleton>(() => new Singleton());

  public static Singleton Instance { get { return lazy.Value; } }

  private Singleton()
  {
  }
}

It's simple and performs well. It also allows you to check whether or not the instance has been created yet with the IsValueCreated property, if you need that.