Getting original class from casted class

Question

For example, I have three classes: Animal, Dog and Cat; where Animal is an abstract class and inherits its properties to Dog and Cat. Say on my program, I have an arbitrary list of things that the user may input (I'm doing this on C# Form). So I store all the inputs, whether they are of class Cat or Dog, into my List<Animal>.

Now I would like to retrieve said instantiated class from List<Animal> and retrieve its original class, whether it's a Cat or a Dog. Is there a way to do that?

Well you can find the type using GetType() but you shouldn't need to. See "Liskov Substitution Principle" https://stackoverflow.com/a/56904/224370 — Ian Mercer, Apr 23 '19 at 04:20
@TheGeneral I want to access the methods available in `Cat` and `Dog` that aren't available in `Animal`. — Richard, Apr 23 '19 at 04:21

score 5 · Accepted Answer · answered Apr 23 '19 at 04:22

5

In latest C# you can do:

Animal animal;
if (animal is Cat cat)
{
   cat.Meow();
}

answered Apr 23 '19 at 04:22

Ian Mercer

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Is there a name for this syntax? – Richard Apr 23 '19 at 04:31
@RichardW the terminology is *Pattern matching*, you can find more information here [is (C# Reference)](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/is) – TheGeneral Apr 23 '19 at 04:37

score 3 · Answer 2 · answered Apr 23 '19 at 04:26

using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Animal> animals = new List<Animal> { new Cat(), new Cat(), new Dog(), new Cat(), new Dog() };

            var dogs = animals.OfType<Dog>().ToList();
            dogs.ForEach(dog => dog.Bark());

            var cats = animals.OfType<Cat>().ToList();
            cats.ForEach(cat => cat.Meow());

            var actualTypes = animals.Select(animal => animal.GetType()).ToList();
        }

        abstract class Animal { }

        class Dog : Animal { public void Bark() { } }

        class Cat : Animal { public void Meow() { } }
    }
}

score 1 · Answer 3 · answered Apr 23 '19 at 04:35

You can use GetType to get the type of the class.

List<Animal> lstA = new List<Animal>();
        lstA.Add(new Cat());
        lstA.Add(new Dog());
        foreach(Animal a in lstA)
        {
            Console.WriteLine("Type of {0}", a.GetType());
        }

abstract class Animal
{}
class Cat : Animal
{}
class Dog : Animal
{}

Getting original class from casted class

3 Answers3