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Published on May 13, 2017 by kudvenkat
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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

All Dot Net and SQL Server Tutorials in English
www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd

All Dot Net and SQL Server Tutorials in Arabic
www.youtube.com/c/KudvenkatArabic/playlists

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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82 Comments on "Singleton Design Pattern"

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Altrix Group
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Altrix Group
2 months 11 days ago

Can you please fix your sound, venkat has good sound and we can hear him very clear. I just can't listen to your videos without having a headache.

venkata narsimha murthy
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venkata narsimha murthy
2 months 17 days ago

can we keep a static class instead of sealed class

venkata narsimha murthy
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venkata narsimha murthy
2 months 17 days ago

Sir in my project they implemented singleton design pattern buy they kept one property of type hash table, Why they had done that?

Amlan D
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Amlan D
3 months 2 days ago

You are good, but where is our favorite Venkat Sir..? 🙂

Carl Andres
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Carl Andres
3 months 27 days ago

"Let's flip to Visual Studio" … reminds me of ol' venkat

Venga Boys
Guest
Venga Boys
3 months 27 days ago

thanks kudvenkat…god bless u

gean kyle leonor
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gean kyle leonor
3 months 28 days ago

Great video but he discuss too fast 🙁 not like Kudvenkat.

Nihal Dev
Guest
Nihal Dev
4 months 11 days ago

Great.

Md Abuzar
Guest
Md Abuzar
4 months 19 days ago

Sir, Could you please tell me what is the real world example in which we must need to create Singleton class or use singleton pattern.

saman khalifa
Guest
saman khalifa
4 months 30 days ago

No matter how intelligent you may sound, I can't take you seriously.

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