Difference Between Static Class And Singleton Instance In C#

In this guide, we are going to explore the variance between the Static Class and Singleton Instance in C#. Prior to delving into their distinctions, it's crucial to comprehend the Static Class and Singleton Instance in C# along with illustrative examples.

Introduction of Static class in C#

One fundamental element for organizing code and encapsulating functionality without the need for instantiation in C# is the "static class". This type of class is essentially a class marked with the static keyword, making it impossible to instantiate like regular classes. Instead, it acts as a container for static members, including fields, methods, properties, and nested types, all of which can be accessed directly using the class name without requiring an instance of the class. Creating utility classes that house common functions or constants, like those used for file manipulation or arithmetic operations, becomes incredibly straightforward with this feature. Static classes are particularly advantageous in scenarios where individual object instances are unnecessary, as they are stateless, lacking instance members and the ability to maintain state.

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Moreover, they provide significant speed improvements as static elements are associated with the class type and do not require object instantiation. Typically, static classes are placed within namespaces for organizational purposes, simplifying access through fully qualified names or by utilizing directives for more efficient usage. While static classes offer advantages, they come with limitations. They cannot include instance constructors, serve as base classes, or inherit from other types aside from Object. All in all, static classes in C# are an effective approach for structuring code, enhancing clarity, and optimizing performance across diverse software development situations.

Example:

Let's consider an example to demonstrate the concept of a static class in C#:

using System;
public static class MathHelper
{
    public static double Square(double number)
    {
        return number * number;
    }
}

class Program
{
    static void Main()
    {
        double input = 5.0;
        double result = MathHelper.Square(input);
        Console.WriteLine($"Square of {input} is {result}");
    }
}

Output:

Square of 5 is 25

Explanation:

In this instance, we make use of the static keyword to build a static class named CalculationUtility. Within the CalculationUtility class, we define a static function called CalculateSquare, which takes a double input parameter and returns the square of the number.

Following that, we invoke the Square method from the MathHelper class within the Main function to calculate the square value of a given integer and display the outcome.

Only static elements (methods, attributes, and variables) are permitted within static classes, such as MathHelper, and these elements cannot be instantiated using the new keyword. Instead, as demonstrated in the Main function, we can directly access their elements by referencing the class name.

Introduction of Singleton instance in C#

A development strategy called the Singleton pattern in C# restricts a class to only one instance throughout the program's execution. This singular object is accessible globally as it belongs to the Singleton instance, streamlining the control over its creation and utilization. The Singleton design, commonly structured with a private constructor and a static method for fetching a unique instance, offers various advantages like centralized configuration handling, resource efficiency, and simplified access to shared resources. It finds utility in scenarios where maintaining a solitary instance ensures uniformity and optimal resource utilization, such as in logging, database connections, and caching mechanisms. While Singleton instances bring numerous advantages, it is crucial to carefully assess potential issues related to thread safety, delayed initialization, and lifecycle management.

Therefore, it is essential to employ the correct practices when constructing a Singleton object in C# to address these concerns and ensure the pattern's effectiveness across the application structure.

Example:

Let's consider a scenario to demonstrate the singleton design pattern in C#:

public class Singleton
{
    // Private static instance variable.
    private static Singleton instance;

    // Private constructor to prevent instantiation from outside.
    private Singleton() { }

    // Public static method to get the instance.
    public static Singleton GetInstance()
    {
        // Lazy initialization: create the instance only if it's null.
        if (instance == null)
        {
            instance = new Singleton();
        }
        return instance;
    }

    // Example method of the Singleton class.
    public void ExampleMethod()
    {
        Console.WriteLine("ExampleMethod called");
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Get the Singleton instance.
        Singleton singletonInstance = Singleton.GetInstance();

        // Call a method on the Singleton instance.
        singletonInstance.ExampleMethod();
    }
}

Output:

ExampleMethod called

Features of the Singleton Class:

Class of Singletons:

The Singleton class is designed to ensure the existence of a single instance throughout the lifetime of the application.

Self-Building Contractor:

Since the Singleton class does not have a public constructor, it prevents other classes from creating instances of it. This restriction ensures that the class cannot be instantiated by any other code, thereby maintaining its Singleton behavior.

Instance Variable Static:

The sole occurrence of the Singleton class is stored in a private static variable named instance.

GetInstance Technique:

Utilize the public static GetInstance function of the Singleton class to obtain the one instance of the class.

It employs lazy initialization, creating an extra instance of the Singleton class if the instance variable is null, and returning the existing instance otherwise.

Main differences between Static Class and Singleton Class in C#

There are key distinctions between Static and Singleton Class in C#. The primary variances between Static and Singleton class include:

To sum up, while both static classes and Singleton instances offer a means of encapsulating code, their functions and attributes differ, as do their instantiation, use, flexibility, thread safety, initialization, memory usage, and lifecycle management aspects.

Conclusion:

In summary, the disparities between a Static class and a Singleton Class in C# have significant implications on design and architecture. While both types prevent instantiation and have sealed contents, Static classes serve as containers for constants, extension methods, or utility functions without the need for state preservation. Conversely, Singleton classes allow instantiation and ensure a single instance throughout the program's execution. They are preferred for tasks like resource management, global state maintenance, and implementing complex behaviors. Static instances offer flexibility by allowing inheritance, interface implementation, and explicit lifecycle control, whereas Static classes prioritize minimalism and thread safety by default.