C#•16mo ago

❔ How does class casting work?

public class Foo
{
    public virtual void Func()
    {
        Console.WriteLine("Foo");
    }
}

public class Boo : Foo
{
    public override void Func() 
    {
        Console.WriteLine("Foo");
    }
}


public class Program
{
    public static void Main()
    {
        var myObjects = new List<Foo>();

        myObjects.Add(new Foo()); // works
        myObjects.Add(new Boo()); // works
        myObjects.Add((Boo)(new Foo())); // how to make this work?

        foreach (var myObject in myObjects)
            myObject.Func();
    }
}

public class Foo
{
    public virtual void Func()
    {
        Console.WriteLine("Foo");
    }
}

public class Boo : Foo
{
    public override void Func() 
    {
        Console.WriteLine("Foo");
    }
}


public class Program
{
    public static void Main()
    {
        var myObjects = new List<Foo>();

        myObjects.Add(new Foo()); // works
        myObjects.Add(new Boo()); // works
        myObjects.Add((Boo)(new Foo())); // how to make this work?

        foreach (var myObject in myObjects)
            myObject.Func();
    }
}

I think code explains itself, but still. How do i cast parent class to child class?

7 Replies

Thinker•16mo ago

(Boo)(new Foo()) will never work because a Foo isn't a Boo

arch_ilOP•16mo ago

but adding Boo to list of Foo works just fine

Thinker•16mo ago

Yes, because a Boo is a Foo myObjects accepts Foo objects, and you can implicitly cast a Boo to a Foo because one inherits from the other But Foo doesn't inherit from Boo, thus you cannot cast from Foo to Boo

arch_ilOP•16mo ago

can i define it somewhere?

Pobiega•16mo ago

you can make a ToBoo method on Foo, or add an explicit conversion but at this point, this sounds like an $xy problem

MODiX•16mo ago

http://xyproblem.info/

The XY Problem

Asking about your attempted solution rather than your actual problem

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ How does class casting work?