派生类和基类引用类型的区别

Question

Guys i want your help please.

We Have This Code:

class Program
{

    static void Main(string[] args)
    {
        Animal pig = new Pig();

        Pig pig2 = new Pig();

        List<Animal> Animals = new List<Animal>();
        Animals.Add(pig);
        Animals.Add(pig2);

        foreach(Animal a in Animals)
        {
            Animal.AnimalSound();
        }
    }
}


class Animal    
{
    public virtual void AnimalSound()
    {
        Console.WriteLine("AnimalSound");
    }
}

class Pig : Animal
{
    public override void AnimalSound()
    {
        Console.WriteLine("wee wee!");
    }
}

My Question is as i instantiate variables pig and pig2 what's the difference Animal pig = new Pig(); and Pig pig2 = new Pig();

Why not declare them both as ReferenceType Pig since Pig is as always Animal????

Answer 1

The difference is, name is not accessible when you do this Animal pig = new Pig(); , but name is accessible in this case Pig pig2 = new Pig(); . You always inherit from base class because you want to use some ready made behavior from parent, and want to add some child specific behavior in child class. Pig is always an animal, but all animals are not Pig.

class Pig : Animal
{
    public string name;

    public override void AnimalSound()
    {
        Console.WriteLine("wee wee!");
    }
}

Answer 2

So you have base class Animal and derived class Pig . So our question can be concluded to what's difference between base and derived classes:

Base class is a class from which other classes are derived.

Derived class is a class that is created on the basis of an existing class. Some features of derived class:

• The derived class inherits almost all of the properties of the base class. Private properties are not accessible due to the accessibility level, however you can use reflection to read their values.
• The derived class can add new members to itself or change base class members.