C# how to create singleton class

4/1/2014·4 min read

This'll show how to cteate singleton class' simple version

Imprement Singleton 1

 class  MySingleton  : Dictionary <int , string >

 		private  static  object  _locker = new  object ();

 		private  static  Dictionary <int , string > _instance;

 		public  static  Dictionary <int , string > Instance

get

 				if  (_instance == null )

 					lock  (_locker)

 						if  (_instance == null )

 							_instance = new  MySingleton ();

 				return  _instance;

 		private  MySingleton()

 			this .Add(0, "name 0" );

 			this .Add(1, "name 1" );

 			this .Add(2, "name 2" );

 			this .Add(3, "name 3" );

 			this .Add(4, "name 4" );

How to call your Singleton class

 	static  void  Main(string [] args)

 			Console .WriteLine(MySingleton .Instance[0]);

 			Console .Read();

Imprement Singleton 2

 	class  MySingleton2

 		private  static  object  _locker = new  object ();

 		private  static  MySingleton2  _instance;

 		private  static  UserInfo  _userinfo;

 		public  static  MySingleton2  Instance

get

 				if  (_instance == null )

 					lock  (_locker)

 						if  (_instance == null )

 							_instance = new  MySingleton2 ();

 				return  _instance;

 		public  MySingleton2()

 			// build your data here

 			_userinfo = new  UserInfo () { Email ="asdf@sdf.com" , FirstName="asd" , Id=1, LastName="asfd"  };

 		public  UserInfo  GetUserInfo()

 			return  _userinfo;

Singleton is very simple to imprement, but it's better not directory calling, it's more safer to do following way.

Create Interface

 	public  interface  IUserInfoService

 		UserInfo  GetUserInfo();

return your Singleton's result from imprement class

 	class  UserInfoService  : IUserInfoService

 		public  UserInfo  GetUserInfo()

 			return  MySingleton2 .Instance.GetUserInfo;

So in this way, at least, when you do your unit-test, you could do Interface Injection to change actual imprementation class to your mock class.

Imprement Singleton 3

  public sealed class Singleton3

         private static volatile Singleton3 instance;

         private static object syncRoot = new Object();

         private static string _getName;

         private Singleton3()

             _getName = "my name";

         public static Singleton3 Instance

get

                 if (instance == null)

                     lock (syncRoot)

                         if (instance == null)

                             instance = new Singleton3();

                 return instance;

         public string MyName

get

                 return _getName;