如何在不使用方法或构造函数的情况下直接访问派生 class 中的基本 class 属性？

Question

class Animal
    {
        public bool isHungry { get; set; }
        public int Age { get; set; }
        public string Name { get; set; }
    }    
class Dog : Animal
    {
        Age = 5; //Gives error, "Age doesnt exist in current context"
        public Dog()
        {
            Age = 5;//Works fine
            Console.WriteLine("Dog");
        }
    }

I want to access the public properties directly, is it not possible?

Answer 1

Code must be within methods - if you want to set a default value for all Dog instances then the constructor is the proper place to do that.

You could make the base property virtual and then override it in Dog with a default value:

class Animal
{
    public bool isHungry { get; set; }
    public virtual int Age { get; set; }
    public string Name { get; set; }
}    
class Dog : Animal
{
    public override int Age {get; set;} = 5; 
    public Dog()
    {
        Console.WriteLine("Dog");
    }
}

but that seems like overkill in this simple example.

Answer 2

D Stanley is totally right. Another way to do it is to use new keyword. This is a little bit cleaner in my opinion but totally depends on the context and problem.

class Dog : Animal
{
    public new int Age = 5;
}

Answer 3

Presumably, not all animals would have the same age ( 5 in this case ). Set your properties via the constructor, or if they have public setters, instantiate an instance of Dog and then set its Age property.

public abstract class Animal
{
    protected Animal()
    {
    }

    public int Age { get; set; }
}    

public class Dog : Animal
{
    public Dog(int age)
    {
        this.Age = age;
    }

    public override string ToString()
    {
        return $"{nameof(Dog)}: {nameof(Age)} - {this.Age}";
    }
}