Question

I have been trying to learn dependency injection but I have 2 errors when I run my code:

1. DependencyInjection.Message.Sms() must declare a body because it is not marked abstract, extern, or partial.
2. Cannot implicitly convert type DependencyInjection.IInterface to DependencyInjection.MyClass. An explicit conversion exists (are you missing a cast?)

Is the code below a good design for DI?

namespace DependencyInjection
{
    public interface IInterface
    {

    }

    public abstract class Message
    {
        public virtual void Sms();
    }

    public class MyClass : Message, IInterface
    {
        public override void Sms()
        {
            Console.WriteLine("Sms gönder.");
        }
    }

    public class ClassManager
    {
        private IInterface _myinterface;


        public MyClass Xyz
        {
            get { return _myinterface; }
            set { _myinterface = value; }
        }

        public ClassManager(IInterface myinterface)
        {
            _myinterface = myinterface;
        }
    }
}

Answer 1

1) DependencyInjection.Message.Sms()’ must declare a body because it is not marked abstract, extern, or partial

Add abstract keyword (and remove virtual) to method declaration:

public abstract void Sms();

2) Cannot implicitly convert type ‘DependencyInjection.IInterface’ to ‘DependencyInjection.MyClass’. An explicit conversion exists (are you missing a cast?)

private IInterface _myinterface;
public MyClass Xyz
{
    get { return _myinterface; }
    set { _myinterface = value; }
}

Xyz has return-type of type MyClass but in get you are returning _myinterface which is of type IInterface.

Change to following:

public IInterface Xyz
{
    get { return _myinterface; }
    set { _myinterface = value; }
}