C# POO

Ex 8 : 
 Polymorphisme 
   
 Ex 9 : 
 namespace test2;

public class Circle
{
 private readonly double radius;
 private readonly double pi = System.Math.PI;

 public Circle(double radius)
 {
 this.radius = radius;
 }

 public double GetArea()
 {
 return pi * radius * radius;
 }

 public double GetPerimeter()
 {
 return 2 * pi * radius;
 }
}

public class Program
{
 static void Main()
 {
 Circle c = new Circle(6.25);
 double area = c.GetArea();
 double perimeter = c.GetPerimeter();
 Console.WriteLine(area); // Doit retourner 122.718463030851.
 Console.WriteLine(perimeter); // Doit retourner 39.2699081698724.
 }
} 
   
   
 Ex 10 : 
 namespace test2;

public class Student : Person
{
 public void GoToClasses()
 {
 Console.WriteLine("I'm going to class.");
 }

 public void DisplayAge()
 {
 Console.WriteLine($"My age is: {this.age} years old");
 }
}

public class Teacher : Person
{
 private string subject;
 
 public void Explain()
 {
 Console.WriteLine("Explanation begins");
 }

 public Teacher(string subject)
 {
 this.subject = subject;
 }
}

public class Person
{
 protected int age;

 public void SetAge(int n)
 {
 this.age = n;
 }

 public virtual void SayHello()
 {
 Console.WriteLine("Hello");
 }
}

public class Test
{
 static void Main()
 {
 Person person = new Person();
 person.SayHello();

 Student student = new Student();
 student.SetAge(15);
 student.SayHello();
 student.GoToClasses();
 student.DisplayAge();

 Teacher teacher = new Teacher("math");
 teacher.SetAge(40);
 teacher.SayHello();
 teacher.Explain();
 }
} 
   
   
   
 BONUS : 
   
 class A
{
 public void Afficher()
 {
 Console.WriteLine("A");
 }
}

class B : A
{
 public new void Afficher()
 {
 Console.WriteLine("B");
 }
}

class C : B
{
 public new void Afficher()
 {
 Console.WriteLine("C");
 }
}

public class Program
{
 static void Main()
 {
 A a = new A();
 B b = new C();
 a.Afficher();
 b.Afficher();
 }
} 
 résultat : 
 A B 
   
 pour avoir AA : il suffit juste de supprimer les 2 "new"