SOLID - Open Closed Principle

Question

What's the Open Closed Principle?

Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.

Example Description:

I aim to enhance my application's functionality by initially implementing a summation operation for two numbers. Over time, I plan to gradually introduce additional operations such as subtraction and division. As time progresses, my goal is to expand the capabilities further, eventually incorporating a division operation.

To achieve this, I will structure my code by creating separate classes and functions for each operation, ensuring a modular and scalable design without the need for constant modifications to the initial class and function.

Example: 

• NOT PREFERRED

• PREFERRED

public abstract class Calculator
{
    public abstract void Operation(double number1, double number2);
}

public class Addition : Calculator
{
    public override void Operation(double number1, double number2)
    {
        Console.WriteLine(number1 + number2);
    }
}

public class Division : Calculator
{
    public override void Operation(double number1, double number2)
    {
        Console.WriteLine(number1 / number2);
    }
}

public class Multiplication : Calculator
{
    public override void Operation(double number1, double number2)
    {
        Console.WriteLine(number1 * number2);
    }
}

 public class Subtraction : Calculator
 {
     public override void Operation(double number1, double number2)
     {
         Console.WriteLine(number1 - number2);
     }
 }

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See Also

• Single Responsibility Principle