My c# derived class can inherit the base class properties and functions, but throws an exception [duplicate]

Question

I have created in my 'main' method an object 'spot' of my base class animal were are 4 properties, a 'Animal' class constructor and a function 'SaySomething'. My object 'spot' passes his parameters to the class constructor 'Animal' for initialization. Furthermore, I have created a derived class 'Dog' which is inheriting the base class 'Animal' properties and the method, and I have created an object 'grover' in my 'main' method, and when I try to access with my 'grover' object the method 'SaySomething' which was inherited, my program throws an exception: 'ConsoleApplication1.Animal' does not contain a constructor that takes 0 arguments, when I try to run the program.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Animal
    {
        public double height { get; set; }
        public double weight { get; set; }
        public string sound { get; set; }
        public string name { get; set; }

        public Animal(double height, double weight, string name, string sound)
        {
            this.height = height;
            this.weight = weight;
            this.name = name;
            this.sound = sound;
        }
        public void SaySomething()
        {
             Console.WriteLine("{0} is {1} inches tall, weighs {2} lbs and likes to say {3}", name, height, weight, sound);
        }

    }

    class Dog : Animal
    {

    }

    class Program
    {
        static void Main(string[] args)
        {
            Animal spot = new Animal(16,10,"spot","woof");
            Dog grover = new Dog();
            grover.SaySomething();
        }
    }
}

I understand that I need to delete my class constructor and spot object parameters and arguments that the program could run. But what is wrong with this code? why my program can't run? And need I choose a different initialization way or it is possible to improve this code for working?

This shouldn't even compile. Animal does not have a parameterless constructor, so the Dog class must call that constructor from it's own constructor. — Silvermind
– Silvermind, Commented Jun 9, 2016 at 22:04
@Silvermind it doesn't compile. The OP is incorrectly identifying that as an "exception". — D Stanley
– D Stanley, Commented Jun 9, 2016 at 22:17

Evan Trimboli · Accepted Answer · 2016-06-09 22:02:57Z

3

Because you don't provide any constructor for Dog, it automatically creates an "empty" constructor, that also tries to call the Animal "empty" constructor. You need to implement a constructor for Dog, or an empty constructor for Animal.

answered Jun 9, 2016 at 22:02

Evan Trimboli

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6 Comments

Erick Over a year ago

All you need to do is add either of the following to the appropriate class: public Dog(){} public Animal(){}

Evan Trimboli Over a year ago

Assuming you want to allow both Dog and Animal to be constructed without parameters...

Erick Over a year ago

True. (Actually, I thought I had an 'or' in between them.) ;)

Alanas Macijauskas Over a year ago

But how should the code look like if I want that the Dog would contain the Animal properties which are initialized in the constructor? I don't want to rewrite the same properties for Dog which are initialized in the Animal constructor.

Evan Trimboli Over a year ago

It's already answered, look at the duplicate.

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