unity example

// usage
            // ...
            IUnityContainer container = new UnityContainer();
            container.RegisterType(typeof (IPhone), typeof (Phone));
            container.RegisterType(typeof (IPda), typeof (Pda));
            container.RegisterType(typeof (ICellPhone), typeof (CellPhone));

            ICellPhone cellPhone = container.Resolve<ICellPhone>()
            // ...

// classes

    public interface IPhone
    {
        void MakeCall(int phoneNumber);
        void AnswerCall();
        void HangUp();
    }

    public interface IPda
    {
        void SendEmail(string[] recipientList, string subject, string message);
        int LookUpContactPhoneNumber(string contactName);
        void SyncWithComputer();
    }

    public interface ICellPhone: IPhone, IPda { }

    public class CellPhone : ICellPhone
    {
        private readonly IPhone _phone;
        private readonly IPda _pda;

        public CellPhone(IPhone phone, IPda pda)
        {
            _phone = phone;
            _pda = pda;
        }

        public void MakeCall(int phoneNumber)
        {
            _phone.MakeCall(phoneNumber);
        }

        public void AnswerCall()
        {
            _phone.AnswerCall();
        }

        public void HangUp()
        {
            _phone.HangUp();
        }

        public void SendEmail(string[] recipientList, string subject, string message)
        {
            _pda.SendEmail(recipientList, subject, message);
        }

        public int LookUpContactPhoneNumber(string contactName)
        {
            return _pda.LookUpContactPhoneNumber(contactName);
        }

        public void SyncWithComputer()
        {
            _pda.SyncWithComputer();
        }
    }

    public class Phone : IPhone
{
    public void MakeCall(int phoneNumber) { // implementation }
    public void AnswerCall() { // implementation }
    public void HangUp() { // implementation }
}

public class Pda : IPda
{
    public void SendEmail(string[] recipientList, string subject, string message) { // implementation }
    public int LookUpContactPhoneNumber(string contactName) { // implementation }
    public void SyncWithComputer() { // implementation }
}