Use the simplest example to understand Singleton pattern)

From the global perspective of the application, if only one instance of the class can be generated, you can consider the singleton mode.

□Real-time loading Singleton Mode

Assign a class instance to a static field of the class.

    class Program
    {
        static void Main(string[] args)
        {
            Logger log = Logger.GetInstance();
            log.WriteToFile();
            Console.Read();
        }
    }
    public class Logger
    {
        private static Logger logger = new Logger();
        private Logger(){}
        public static Logger GetInstance()
        {
            return logger;
        }
        public void WriteToFile()
        {
Console. writeline ("the error is written to the file ~~ ");
        }
    }

 

□Delayed loading Singleton Mode

The instance of the class is not generated until the static method of the class is called.

    public class Logger
    {
        private static Logger logger = null;
        private Logger(){}
        public static Logger GetInstance()
        {
            if (null == logger)
            {
                logger = new Logger();
            }
            return logger;
        }
        public void WriteToFile()
        {
Console. writeline ("the error is written to the file ~~ ");
        }
    }   

□Thread-safe Singleton Mode

Until the static method of the class is called, ensure that only one thread enters the instance of the generated class.

   public class Logger
    {
        private static Logger logger = null;
        private static object lockObj = new object();
        private Logger(){}
        public static Logger GetInstance()
        {
            lock (lockObj)
            {
                if (logger == null)
                {
                    logger = new Logger();
                }
                return logger;
            }
        }
        public void WriteToFile()
        {
Console. writeline ("the error is written to the file ~~ ");
        }
    }

 

Summary: static Singleton-type private fields and private constructor. Acquiring Singleton is a necessary element of Singleton mode.

Use the simplest example to understand Singleton pattern)