C# Tutorial 9
In this part of my C# tutorial we’ll be covering Abstract Classes, Virtual Methods, Abstract Methods, Override, Base Classes, Is, As, Casting and more about Polymorphism.
Thank you so much for joining me. I greatly appreciate it! All of the code along with a transcript / cheat sheet can be found after the video below to help you learn.
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Code & Transcript
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// ---------- Shape.cs ---------- using System; // Very often you want to define a // class that you don't want to be // instantiated. In that case an // Abstract class may be the way to // go. namespace CSharpTutA.cs { abstract class Shape { public string Name { get; set; } // You can define non-abstract // methods in an abstract class public virtual void GetInfo() { Console.WriteLine($"This is a {Name}"); } // We want subclasses to override // this method so mark it as abstract // You can only make abstract methods // in abstract classes public abstract double Area(); } } // ---------- Circle.cs ---------- using System; namespace CSharpTutA.cs { class Circle : Shape { public double Radius { get; set; } public Circle(double radius) { Name = "Circle"; Radius = radius; } public override double Area() { return Math.PI * (Math.Pow(Radius, 2.0)); } // You can replace the method using override public override void GetInfo() { // Execute the base version base.GetInfo(); Console.WriteLine($"It has a Radius of {Radius}"); } } } // ---------- Rectangle.cs ---------- using System; namespace CSharpTutA.cs { class Rectangle : Shape { public double Length { get; set; } public double Width { get; set; } public Rectangle(double length, double width) { Name = "Rectangle"; Length = length; Width = width; } public override double Area() { return Length * Width; } // You can replace the method using override public override void GetInfo() { // Execute the base version base.GetInfo(); Console.WriteLine($"It has a Length of {Length} and Width of {Width}"); } } } // ---------- Program.cs ---------- using System; // This time we cover Abstract Classes, Abstract // Methods, Base Classes, Is, As, Casting and // more about Polymorphism namespace CSharpTutA.cs { class Program { static void Main(string[] args) { // We can store our shapes in // a Shape array as long as it // contains subclasses of Shape Shape[] shapes = {new Circle(5), new Rectangle(4,5)}; // Cycle through shapes and print // the area foreach(Shape s in shapes) { // Call the overidden method s.GetInfo(); Console.WriteLine("{0} Area : {1:f2}", s.Name, s.Area()); // You can use as to check if an // object is of a specific type Circle testCirc = s as Circle; if(testCirc == null) { Console.WriteLine("This isn't a Circle"); } // You can use is to check the data // type if(s is Circle) { Console.WriteLine("This isn't a Rectangle"); } Console.WriteLine(); } // You can store any class as a base // class and call the subclass methods // even if they don't exist in the base // class by casting object circ1 = new Circle(4); Circle circ2 = (Circle)circ1; Console.WriteLine("The {0} Area is {1:f2}", circ2.Name, circ2.Area()); Console.ReadLine(); } } } |
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