this和base

this，用于类中，指代这个类

base，用于子类中，用于指代父类

class Animal
{
  string str = "Animal Say!";
  public virtual void Say()
  {
    Console.WriteLine(this.str);
  }
}

class Cat: Animal
{
  void Say()
  {
    base.Say();
  }
}

public class App
{
  static void Main(string[] args)
  {
    Animal _animal = new Animal();
    _animal.Say();

    Cat cat = new Cat();
    cat.Say();

    Console.ReadKey();
  }
}