Exploring the Singleton Pattern

In some situations, we want to have an instance of a class with public instance methods (not static methods), but never more than one instance of our class.

Exploring the Singleton pattern.

In some situations, we want to have an instance of a class with public instance methods (not static methods), but never more than one instance of our class. An example might be where hardware is being accessed, such as an audio card, and we want to ensure that for thread safety that we never have more than one instance of the native code handle to the resource alive.

This is where the Singleton pattern comes into play. Here is a simplified console app example of a Singleton class "Utils" with an ID field that
is constructed solely to show that we can never have more than one instance of our class. Start a new Console application and paste all the code
below into it:

using System;
namespace SingletonDemo
{
class Tester
{
[STAThread]
static void Main(string[] args)
{
Utils u = Utils.Instance ;
Console.WriteLine("First Instance ID: " +u.Id.ToString());
// Sleep the thread for a second just to prove the single instance ID doesn't change
System.Threading.Thread.Sleep(1000);
Utils u2 = Utils.Instance ;
Console.WriteLine("Second Instance ID: "+u2.Id.ToString());
Console.WriteLine("Non-static public Method Call: "+ u2.SayHello("test"));
Console.ReadLine();
}
}

public sealed class Utils
{
private Utils()
{
this.Id= new System.Random((int)DateTime.Now.Ticks ).Next();
}
public static readonly Utils Instance = new Utils();
public int Id;
public string SayHello(string input)
{
return "hello, " +input;
}
}
}


Submission Date:  9/23/2005 3:13:39 PM
Submitted By:  Peter Bromberg
My Home Page:  http://www.eggheadcafe.com