CODEWITHSUNDEEP
c#instance
AnonBird
AnonBird

Reputation: 656

Convert Class<Object> to Class<Interface>

I have a class Dog implementing an interface IAnimal and an IDbSet<Dog> DogSet.

I have the following prototype : MyMethod(IDbSet<IAnimal> AnimalSet)

When trying to do MyMethod(DogSet); I have an error at compilation saying it's not possible to explicitly cast IDbSet<Dog> to IDbSet<IAnimal>

If I try to cast it using MyMethod((IDbSet<IAnimal>)DogSet), I have an error at runtime because it fails to cast.

Why can't I cast it since Dog implement IAnimal ?

Code :

public interface IAnimal{
    public String Libelle { get; }
}

public partial class Dog : IAnimal{
    public String Libelle {
        get {
            return "Hello World";
        }
    }
}

// Can't convert from 'System.Data.Entity.IDbset<Models.Dog>' to 'System.Data.Entity.IDbSet<Interfaces.IAnimal>'
public abstract MyClass : MyAbstractClass{
    public MyClass(IModel dbContext) : base(dbContext, dbContext.DOG_IDBSET) { }
}

public abstract class MyAbstractClass{
    public MyAbstractClass(Imodel dbContext, IDbSet<IAnimal>){ }
}

Edited code :

// Can't convert from 'System.Data.Entity.IDbset<Models.Dog>' to 'System.Data.Entity.IDbSet<T>'
public abstract MyClass<T> : MyAbstractClass<T> where T : Dog, IAnimal
{
    public MyClass(IModel dbContext) : base(dbContext, dbContext.DOG_IDBSET) { }
}

public abstract class MyAbstractClass<T> where T : Dog, IAnimal
{
    public MyAbstractClass(Imodel dbContext, IDbSet<T>){ }
}

Upvotes: 2

Views: 197

Answers (1)

kaffekopp
kaffekopp

Reputation: 2619

By setting generic constraints to require a class implementing interface IAnimal you should be able to do this:

public void MyMethod<T>(DbSet<T> animals) where T : class, IAnimal
{
    ...
}

...and call as:

MyMethod(DogSet);

Upvotes: 5

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