A static class is one that has only static methods, for which a better word would be "functions". The design style embodied in a static class is purely procedural.
Singleton, on the other hand, is a pattern specific to OO design. It is an instance of an object (with all the possibilities inherent in that, such as polymorphism), with a creation procedure that ensures that there is only ever one instance of that particular role over its entire lifetime.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace SingletonVsStaticClass
{
class SomeClass
{
public int ABC;
}
public sealed class SingletonSampleClass
{
static SingletonSampleClass _instance;
public static SingletonSampleClass Instance
{
get { return _instance ?? (_instance = new SingletonSampleClass()); }
}
private SingletonSampleClass() { }
public string Message { get; set; }
}
static public class StaticSampleClass
{
private static readonly int SomeVariable;
//Static constructor is executed only once when the type is first used.
//All classes can have static constructors, not just static classes.
static StaticSampleClass()
{
SomeVariable = 1;
//Do the required things
}
public static string ShowValue()
{
return string.Format("The value of someVariable is {0}", SomeVariable);
}
public static string Message { get; set; }
}
class Program
{
static void Main(string[] args)
{
//Normal class instantiation and usage
var someClass = new SomeClass {ABC = 5};
Console.WriteLine("Normal class usage: "+someClass.ABC);
//Static Class instantiation
string returnValue = StaticSampleClass.ShowValue();
Console.WriteLine("Static class usage: " + returnValue);
//Singleton class instantiation
var singletonSampleClass = SingletonSampleClass.Instance;
singletonSampleClass.Message = "Hello";
Console.WriteLine("Singleton class usage: " + singletonSampleClass.Message);
//Test the instances if are equal
var anotherSingletonSampleClass = SingletonSampleClass.Instance;
Console.WriteLine("Checking if both instances are same: "+ singletonSampleClass.Equals(anotherSingletonSampleClass) );
Console.Read();
}
}
}
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