public void ShouldFailCovariant()
{
Animal[] cats = new AnimalCat[3];
cats[0] = new AnimalCat { Name = "Tigrus" };
cats[1] = new AnimalCat { Name = "Garfield" };
Assert.Throws<ArrayTypeMismatchException>(() => { cats[2] = new AnimalPerson(); });
var cat = cats[1];
Assert.IsAssignableFrom<AnimalCat>(cat);
Assert.IsNotAssignableFrom<Animal>(cat);
#if NotCompilable
AnimalCat[] otherCats = new Animal[2];
therCats[0] = new Animal();
List<AnimalCat> otherCatsList = new List<Animal>();
#endif
}
public void ShouldSuccessfullyCovariant()
{
Animal[] persons = new Animal[4];
persons[0] = new Animal();
persons[1] = new AnimalCat();
persons[2] = new AnimalPerson();
var person = (AnimalPerson)persons[2];
Assert.IsAssignableFrom<AnimalPerson>(person);
Assert.IsNotAssignableFrom<Animal>(person);
List<Animal> personsList = new List<Animal>();
personsList.Add(new Animal());
personsList.Add(new AnimalCat());
personsList.Add(new AnimalPerson());
var personListItem = personsList.Last();
Assert.IsAssignableFrom<AnimalPerson>(personListItem);
Assert.IsNotAssignableFrom<Animal>(personListItem);
}