Inheritance

Constructor

• Base class constructors are called first.

• Base class constructors are not inherited.

public class Person
{
  private string _name;

  public Person(string name)
  {
    this._name = name;
  }
}

public class Customer : Person
{
  public Customer(string name)
    : base(name)
  {
    // TODO
  }
}

base() will call the constructors of the base class before initialization.

Upcasting & Downcasting

• Upcasting: convert from a derived class to a base class.
• Downcasting: convert from a base class to a derived class.

Upcasting

Person a = new Person("a");
Customer b = a; // safe, no extra action

Downcasting

Person a = new Person("a");
Customer b = a;

Person c = (Person)b;

as keyword

Customer c = person as Customer;

is keyword

if (person is Customer)
{
  Customer c = person;
}