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Published on May 13, 2017 by kudvenkat

Text version of the video
csharp-video-tutorials.blogspot.com/2017/05/singleton-design-pattern.html

Slides
csharp-video-tutorials.blogspot.com/2017/05/singleton-design-pattern_13.html

Design Patterns Tutorial

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In this tutorial we will discuss
1. What is Singleton Design Pattern
2. Singleton as Creational Pattern
3. Implementation Guidelines
4. How do we implement a Singleton class

This is continuation to Part 1 of Design Patterns Tutorial. So please watch Part 1 before proceeding.

Singleton Pattern belongs to Creational type pattern. As discussed in our previous video, Gang of four have defined five design patterns that belongs to creational design type category. Singleton is one among them and the rest are Factory, Abstract Factory, Builder and Prototype patterns. As the name implies, creational design type deals with object creation mechanisms. Basically, to simplify this, creational pattern explain us the creation of objects in a manner suitable to a given situation.

Singleton design pattern is used when we need to ensure that only one object of a particular class is Instantiated. That single instance created is responsible to coordinate actions across the application.

Advantages and Guidelines for Singleton implementation.

Concurrent access to the resource is well managed by singleton design pattern.

As part of the Implementation guidelines we need to ensure that only one instance of the class exists by declaring all constructors of the class to be private. Also, to control the singleton access we need to provide a static property that returns a single instance of the object.

Singleton Class Implementation Example

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
// First version of Singleton demo
namespace SingletonDemo
{
class Program
{
static void Main(string[] args)
{
/*
* Assuming Singleton is created from employee class
* we refer to the GetInstance property from the Singleton class
*/
Singleton fromEmployee = Singleton.GetInstance;
fromEmployee.PrintDetails(“From Employee”);
/*
* Assuming Singleton is created from student class
* we refer to the GetInstance property from the Singleton class
*/
Singleton fromStudent = Singleton.GetInstance;
fromStudent.PrintDetails(“From Student”);

Console.ReadLine();
}
}
}

Singleton.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace SingletonDemo
{
/*
* Sealed ensures the class being inherited and
* object instantiation is restricted in the derived class
*/
public sealed class Singleton
{
private static int counter = 0;

/*
* Private property initilized with null
* ensures that only one instance of the object is created
* based on the null condition
*/
private static Singleton instance = null;

/*
* public property is used to return only one instance of the class
* leveraging on the private property
*/
public static Singleton GetInstance
{
get
{
if (instance == null)
instance = new Singleton();
return instance;
}
}
/*
* Private constructor ensures that object is not
* instantiated other than with in the class itself
*/
private Singleton()
{
counter++;
Console.WriteLine(“Counter Value ” + counter.ToString());
}
/*
* Public method which can be invoked through the singleton instance
*/
public void PrintDetails(string message)
{
Console.WriteLine(message);
}
}
}

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54 Comments on "Singleton Design Pattern"

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Marcin Grygierczyk
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Marcin Grygierczyk
14 days 6 hours ago

Awesome! Waiting for more 🙂 Thanks!

Avish MSD
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Avish MSD
7 days 22 hours ago

Thank you so much. We are trying our best to post them as many as we can.

Shreepad Deshpande
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Shreepad Deshpande
14 days 7 hours ago

thank you Avish. kindly bring up next video ASAP as delays fades up some learning from last video.Nice video.

Anas Al-Qudah
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Anas Al-Qudah
14 days 7 hours ago

great video, thanks

Deepak Gupta
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Deepak Gupta
14 days 9 hours ago

thank you so much for creating such a valuable video for us.

Farooq Md
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Farooq Md
14 days 10 hours ago

I have been waiting for long time for design pattern videos, Thank you sooo much for starting this series

ShellmanDeluxe
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ShellmanDeluxe
14 days 10 hours ago

Great video, i'm looking forward to see more of this series 🙂

Avish MSD
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Avish MSD
7 days 22 hours ago

Thank you so much. We are trying our best to post them as many as we can.

Nitin Verma
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Nitin Verma
14 days 12 hours ago

Keep going sir.. and please upload some Data Structure videos…….

Parth Mashroo
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Parth Mashroo
14 days 12 hours ago

Finally design patterns started waiting for this series since angular……

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