How to list all items when using inheritance? - asp.net-core

Question

I'm trying to work with inheritance. I have three models
class Animal {string name;}
class Cat : Animal {int meowPerHour}
class Dog : Animal {bool mixedBreed}
Ef core has created a Discriminator column and I can list Cats or Dogs seperately and I can create new items.
The problem is that I'd like to list both all animals with their respective unique properties. E.g. if the row is a Cat, print meowPerHour. But the mewPerHour is not a property or method in the Animal Class. I'm using the code below to print all animals.
public IList<Animal> Aniamls { get;set; }
public async Task OnGetAsync()
{
Animals = await _context.Animal.ToListAsync();
}
How may I solve this?

Answer 1

You can use following approach but be careful about this approach is eagerly loading all Animals and may not be suits best for all your cases.
public IEnumerable<IAnimal> GetAllAnimals()
{
List<IAnimal> allAnimals = GetAllEntriesByEntityInterface<IAnimal>();
return allAnimals;
}
Method for combining all entitties in one list
private List<T> GetAllEntries<T>() where T : class
{
List<IQueryable<T>> sets = typeof(T).IsInterface ? GetAllSetsByInterface<T>() : GetAllSetsByBaseClass<T>();
List<T> allEntries = new List<T>();
foreach (var item in sets)
{
allEntries.AddRange(item.ToList());
}
return allEntries;
}
Here we are gettings all Sets of entities implementing generic class of T. This method may be useful if you need to work with Interfaces.
private List<IQueryable<T>> GetAllSetsByInterface<T>() where T : class
{
var types = context.Model.GetEntityTypes().Select(t => t.ClrType).ToList().Where(t => t.GetInterfaces().Any(i => i == typeof(T))).ToList();
var sets = types.Select(type =>
context.GetType()
.GetMethod("Set")
.MakeGenericMethod(type)
.Invoke(context, null)
as IQueryable<T>
).ToList();
return sets;
}
And method for fetching all Sets of entities derived from generic class of T
private List<IQueryable<T>> GetAllSetsByBaseClass<T>() where T : class
{
var types = context.Model.GetEntityTypes().Select(t => t.ClrType).Where(x => x.IsSubclassOf(typeof(T))).ToList();
var sets = types.Select(type =>
context.GetType()
.GetMethod("Set")
.MakeGenericMethod(type)
.Invoke(context, null)
as IQueryable<T>
).ToList();
return sets;
}