Singleton Pattern in C#

Singleton pattern

akshay babannavar

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Oct 9, 2021

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Singleton design pattern is creational pattern among GoF (Gang of Four) design patterns. It restricts instantiation of class to a single object.

Singleton pattern as code

using System.IO;
using System;public sealed class Singleton
{   //private fields
   private static Singleton _instance = null;
   private static object _lockSingletonObj = new object();   //private constructor
   private Singleton() { }
   
   //public property
   public static Singleton Instance
   {
     get
       {
        lock (_lockSingletonObj)
        {
          if (_instance == null)
          _instance = new Singleton();
          return _instance;
        }
   }
} //pubic method
 public void GetData()
 {
  Console.WriteLine(“Data”);
 }
}class Program
{
  static void Main(string[] args)
  {
   //how to call singleton instance
   //below line will create a single instance and call GetData   
   //method
   Singleton.Instance.GetData();
   Console.ReadLine();
  }
}

Singleton pattern usage

• Only one instance of a class is required
• Common data to be shared across application
• Reduce instantiating heavier objects repeatedly such as Database connection, I/O operations

P.S. Use singleton only when we are absolutely certain that we need it. There are always better alternatives such as Dependency Injection or static class