獨體模式(Singleton)

• 保證一個類別僅有一個實體，並提供一個存取它的全域訪問點

懶漢式獨體類別 (Double-Check Locking)

using System;

namespace DPExample
{
 public class Singleton
 {
  private static Singleton instance;
  private static readonly object syncRoot = new object();

  private Singleton ()
  {
  }

  public static Singleton GetInstance ()
  {
   if (instance == null)
   {
    lock (syncRoot)
    {
     if (instance == null)
     {
      instance = new Singleton ();
     }
    }
   }

   return instance;
  }
 }
}

餓漢式獨體類別

using System;

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

  private Singleton ()
  {
  }

  public static Singleton GetInstance ()
  {
   return instance;
  }
 }
}