Four implementation methods of the "Singleton" Mode in C #

You must have used or read"Singleton.
The following three implementation methods are provided, and the advantages and disadvantages are given respectively.

 

Method 1:

 

 public sealed class Singleton
{
   private static readonly Singleton instance = new Singleton();
   
   private Singleton(){}

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

Advantages:Simple and clear
Disadvantages:Resource Consumption

 

 

Method 2:

 

 public sealed class ClassicSingleton
{
    private static ClassicSingleton instance;
    private static object syncRoot = new Object();

    private ClassicSingleton() { }

    public static ClassicSingleton Instance
    {
        get
        {
            if (instance == null)
            {
                lock (syncRoot)
                {
                    if (instance == null)
                    {
                        //...custom code
                        instance = new ClassicSingleton();
                    }
                }
            }

            return instance;
        }
    }
}

Advantages:Save resources
Disadvantages:Lengthy code

 

 

Method 3:

 

 public sealed class Singleton
{
    static Singleton(){Instance = new Singleton();}

    private Singleton(){}

    public static Singleton Instance{get; private set;}
}

 

 

 

 

Advantages:Resource Saving and simplicity
Disadvantages:Thread Security

 

Method 4:

 

 public class Singleton
{
    private static Singleton instance;
    // Added a static mutex for synchronising use of instance.
    private static System.Threading.Mutex mutex;
    private Singleton() { }
    static Singleton()
    {
        instance = new Singleton();
        mutex = new