Casting with as and is operators in C Sharp (C#) - Mini Project: Build & Apply

Casting with as and is operators

📖 Scenario: Imagine you have a list of different shapes, but you want to work only with circles. You need to check if each shape is a circle and then get its radius.

🎯 Goal: You will create a list of shapes, check each shape's type using is and as operators, and print the radius of circles.

📋 What You'll Learn

Create a list called shapes with different shape objects

Create a variable called circleCount to count circles

Use a foreach loop with is operator to count circles

Use a foreach loop with as operator to print circle radii

💡 Why This Matters

🌍 Real World

In real programs, you often have collections of different objects and need to work with only some types safely.

💼 Career

Understanding type checking and casting is important for writing safe and clear code in many C# applications.

1

Create the shapes list

Create a list called shapes containing these objects: a Circle with radius 5, a Rectangle with width 4 and height 6, and another Circle with radius 3.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Shape {}

class Circle : Shape {
    public int Radius { get; }
    public Circle(int radius) { Radius = radius; }
}

class Rectangle : Shape {
    public int Width { get; }
    public int Height { get; }
    public Rectangle(int width, int height) { Width = width; Height = height; }
}

class Program {
    static void Main() {
        // Create the shapes list here
        
    }
}

Need a hint?

Use List<Shape> and add the objects inside curly braces.

2

Create a circle counter

Create an integer variable called circleCount and set it to 0 to count how many circles are in the list.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Shape {}

class Circle : Shape {
    public int Radius { get; }
    public Circle(int radius) { Radius = radius; }
}

class Rectangle : Shape {
    public int Width { get; }
    public int Height { get; }
    public Rectangle(int width, int height) { Width = width; Height = height; }
}

class Program {
    static void Main() {
        List shapes = new List {
            new Circle(5),
            new Rectangle(4, 6),
            new Circle(3)
        };
        // Create circleCount variable here
        
    }
}

Need a hint?

Use int circleCount = 0; to start counting circles.

3

Count circles using is operator

Use a foreach loop with variables shape to go through shapes. Inside the loop, use the is operator to check if shape is a Circle. If yes, increase circleCount by 1.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Shape {}

class Circle : Shape {
    public int Radius { get; }
    public Circle(int radius) { Radius = radius; }
}

class Rectangle : Shape {
    public int Width { get; }
    public int Height { get; }
    public Rectangle(int width, int height) { Width = width; Height = height; }
}

class Program {
    static void Main() {
        List shapes = new List {
            new Circle(5),
            new Rectangle(4, 6),
            new Circle(3)
        };
        int circleCount = 0;
        // Count circles using is operator
        
    }
}

Need a hint?

Use if (shape is Circle) inside the loop to check the type.

4

Print circle radii using as operator

Use a foreach loop with variable shape to go through shapes. Inside the loop, use the as operator to cast shape to Circle and store it in a variable called circle. If circle is not null, print "Circle radius: " followed by circle.Radius. Finally, print "Total circles: " followed by circleCount.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Shape {}

class Circle : Shape {
    public int Radius { get; }
    public Circle(int radius) { Radius = radius; }
}

class Rectangle : Shape {
    public int Width { get; }
    public int Height { get; }
    public Rectangle(int width, int height) { Width = width; Height = height; }
}

class Program {
    static void Main() {
        List shapes = new List {
            new Circle(5),
            new Rectangle(4, 6),
            new Circle(3)
        };
        int circleCount = 0;
        foreach (Shape shape in shapes) {
            if (shape is Circle) {
                circleCount++;
            }
        }
        // Print circle radii using as operator
        
    }
}

Need a hint?

Use Circle circle = shape as Circle; and check if circle != null before printing.