Design Patterns C#

A design pattern provides a framework for building an application. Design patterns makes the design process cleaner and more efficient. You can use existing design patterns to make templates for your objects and allowing you to build software faster. 

• Singleton
• Factory

Singleton pattern C# Example

Singleton is used to restrict instantiation of a class to one object. In this way we ensure that the class has only one instance.

When to use?

Usually singletons are used for centralized management  and provide a global point of access to themselves.

• logging
• configuration
• resources

Example

using System;

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1

{
    class Singleton
    {
        private static Singleton instance;
        protected Singleton()
        {
          // protected constructor
        }

 

             public static Singleton GetInstance()

        {

            if (instance == null)

            {

                lock (typeof(Singleton))

                {

                    instance = new Singleton();

                }

            }

            return instance;

        }

    }

    public partial class Form1 : Form

    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            // Singleton st = new Singleton(); Error 'WindowsFormsApplication1.Singleton.Singleton()' is inaccessible due to its protection level 
            Singleton st1 = Singleton.GetInstance();
            Singleton st2 = Singleton.GetInstance(); // st2=st1
        }
    }
}