c# abstract class
abstract class Shape
{
public abstract int GetArea();
}
class Square : Shape
{
int side;
public Square(int n) => side = n;
// GetArea method is required to avoid a compile-time error.
public override int GetArea() => side * side;
static void Main()
{
var sq = new Square(12);
Console.WriteLine($"Area of the square = {sq.GetArea()}");
}
}
// Output: Area of the square = 144
// ------------------- ABSTRACT vs INTERFACES ------------------------ //
// Both are used to define the architecture of the application
// ---------- ABSTRACT CLASS --------- //
// -> The methods can have an implementation (be defined)
// -> It's elements are private by default
// -> It can contain fields
// -> It can inherit from another abstract class or interface
// -> It can have abstract and non-abstract methods. The abstract classes have to be implemented in the child class.
public abstract class AbsParent {
private int count = 0;
public void foo1()
{
Console.WriteLine("Hi there, I'm a normal method that will be inherited!");
}
public abstract void foo2(); // You can't have an implementation for this abstract method
public virtual void foo3()
{
Console.WriteLine("Hi there, I'm a virtual method!");
}
}
// --------- INTERFACES --------- //
// -> It's not a class, it's an entity
// -> The methods can't have an implementation
// -> It's elements are public by default and can't have acesso modifiers
// -> It can't contain fields like for example, "private int count", but it can contain properties
// -> It can only inherit from another interface
// -> A class can inherit from multiple interfaces
// -> A class inheriting from an interface, has to implement all it's methods
public interface IParent {
string myProterty{get; set;}
void foo1(); // You can't have an implementation for these methods
void foo2();
}
// -------- INHERITANCES --------- //
// class 'AbsParent' inherit in child class 'Child1'
public class Child1 : AbsParent {
public override void foo2() // The implementation of the AbsParent abstract methods is mandatory
{
Console.WriteLine("Only in the child/derived class, can I be defined!");
}
public override void foo3()
{
Console.WriteLine("Class name is Child1");
}
}
// class 'IParent' inherit in another child class 'Child2'
public class Child2 : IParent {
public void foo1() // The implementation of all the IParent methods is mandatory
{
Console.WriteLine("Only in the child/derived class, can I be defined!");
}
public void foo2()
{
Console.WriteLine("Only in the child/derived class, can I be defined!");
}
}
// ---------- MAIN --------- //
public class main_method {
// Main Method
public static void Main()
{
AbsParent obj = new AbsParent(); // ERROR!! You can't create an object of an abstract class
// it is used only for inheritance purposes. The same logic
// goes to interfaces.
}
}
abstract class Shape
{
public abstract int GetArea();
}
class Square : Shape
{
int side;
public Square(int n) => side = n;
// GetArea method is required to avoid a compile-time error.
public override int GetArea() => side * side;
static void Main()
{
var sq = new Square(12);
Console.WriteLine($"Area of the square = {sq.GetArea()}");
}
}
// Output: Area of the square = 144
