Adapter Pattern in C#

Introduction

Most of you might have heard about the Adapter Pattern. It is a pattern commonly used in our applications, but without knowing it. The Adapter Pattern is one among the 23 Design Patterns.

Challenge

You are working on a Square class. You need to find the Area of it using the Calculator class. But the Calculator class only takes the Rectangle class as input. How to solve this scenario.

Definition

Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.

Implementation

Following are the class definitions for Rectangle and Calculator.

public class Rectangle
{
    public int Width;   // Width of the rectangle
    public int Height;  // Height of the rectangle
}
public class Calculator
{
    public int GetArea(Rectangle rectangle)
    {
        int area = rectangle.Width * rectangle.Height;  // Calculate area as width times height
        return area;  // Return the calculated area
    }
}

As we cn see from the above example, an instance of a Rectangle is needed to calculate the area. If we have a square class of definition below, the calculation cannot be done.

public class Square
{
    public int Size;  // Size represents the side length of the square
}

Here we have to create a new CalculatorAdapter to get the work done.

public class CalculatorAdapter
{
    public int GetArea(Square square)
    {
        Calculator calculator = new Calculator();  // Create an instance of the Calculator class       
        Rectangle rectangle = new Rectangle();  // Create an instance of the Rectangle class
        rectangle.Width = rectangle.Height = square.Size;  // Set the width and height to the square's size        
        int area = calculator.GetArea(rectangle);  // Calculate the area using the Calculator class        
        return area;  // Return the calculated area
    }
}

The CalculatorAdapter performs the following functions.

• Takes the Square parameter
• Convert Square to Rectangle
• Call the original Calculator.GetArea() method
• Return the value received

The invoking code is shown below.

// Create Square class and assign Size from UI
Square square = new Square();
square.Size = SquarePanel.Width;
// Use Adapter to calculate the area
CalculatorAdapter adapter = new CalculatorAdapter();
int area = adapter.GetArea(square);
// Display the result back to UI
ResultLabel.Text = "Area: " + area.ToString();

On running the sample application, we can see the following results.

Note. We can have other examples, including Interfaces, to show the above pattern. For simplicity, I have avoided the interfaces. In real life, the AC to DC adapter is an example of the Adapter pattern as it makes the incompatible device and power supply work together.

Summary

In this article, we have explored the Adapter pattern. This pattern is useful in scenarios where incompatible types are dealt with. The associated source code contains the example application we have discussed.