CODEWITHSUNDEEP
c#
RotatingWheel
RotatingWheel

Reputation: 1051

Cannot implicitly convert type for interface

There is some duplicate of similar thread in stackoverflow but this is not exact same, so I post here again. Let's consider the following example.

  public interface ILeft
    {
        void Move();
    }

    public class MoveableOject : ILeft
    {
        //without public we get an error
        public void Move()
        {
            Console.WriteLine("Left moving");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            MoveableOject mo = new MoveableOject();
            mo.Move();
            Console.ReadKey();
        }
    }

All are fine. Now let's consider the explicit implementation of ILeft. Why does the commented line give above error message?

 class MoveableOject : ILeft
{
    void ILeft.Move()
    {
        Console.WriteLine("Left moving");
    }
}

class Program
{
    static void Main(string[] args)
    {
        MoveableOject mo = new MoveableOject();
       // MoveableOject moWithErrorObject = (ILeft) new MoveableOject(); <--
        ((ILeft)mo).Move();
        ((ILeft)new MoveableOject()).Move();

        Console.ReadKey();
    }
}

Edit: 8th Nov/2015 MoveableOject in the error statement should be ILeft understandable, mistakenly I put it there. Why I post it the reason I could not explain it, let's use the object and passed to a method in the following way.

public static void ExpectDerivedPassedDerived(MoveableOject passedObject)
{
    passedObject.Move();
}

Now if I call the method from Main should it work? But it does not because I have explicit implementation but if I implement with public keyword then this will be fine, I was looking an explanation of this.

 ExpectDerivedPassedDerived(mo);  //mo is MoveableOject type

Upvotes: 1

Views: 9355

Answers (2)

xZ6a33YaYEfmv
xZ6a33YaYEfmv

Reputation: 1816

The error that you are observing has nothing to do with explicit implementation of ILeft. Actually that's because of assignment compatibility. We can only assign more derived objects to less derived objects, not vice versa.

You cannot do:

MoveableOject moWithErrorObject = (ILeft) new MoveableOject();

As MoveableOject is more derived than it's parent ILeft.

You can get some details here.

Upvotes: 2

Gian Paolo
Gian Paolo

Reputation: 4249

You create a new MoveableOject, cast it as ILeft, and then you try to assing the ILeft you got from cast to a MoveableObject reference. Compliler disagree, as expected

Ileft iLeftReference = getILeft();
MoveableOject mObj = iLeftReference; // same error

Upvotes: 2

Related Questions