Csharp/CSharp Tutorial/Design Patterns/Singleton Pattern

Singleton Pattern

<source lang="csharp">using System; public class SingletonClass {

   private static SingletonClass instance;
   static SingletonClass()
   {
       instance = new SingletonClass();
   }
   private SingletonClass() { }
   public static SingletonClass Instance
   {
       get { return instance; }
   }
   public void SomeMethod1() { }
   public void SomeMethod2() { }

} public class MainClass {

   public static void Main()
   {
       SingletonClass s = SingletonClass.Instance;
       s.SomeMethod1();
       SingletonClass.Instance.SomeMethod2();
   }

}</source>

Singleton Pattern 2

<source lang="csharp">using System;

 class Client
 {
   static void Main(string[] args)
   {
     try{
       Engine eng = Engine.GetEngine();
     }catch (Exception e){
       Console.WriteLine(e.Message);
     }
     
     try{
       Engine eng = Engine.GetEngine();
     }catch (Exception e){
       Console.WriteLine(e.Message);
     }
   }
 }
 sealed class Engine
 {
   private static bool instanceFlag = false;
   public static Engine GetEngine()
   {
     if (!instanceFlag)
     {  
       instanceFlag = true;
       return new Engine();
     }else{
       throw new Exception("An engine has already been created!");
     }
   }
   private Engine()
   {
     Console.WriteLine("An Engine");
   }
 }</source>