using System;

​

namespace ExternalClasses

{

    public class A

    {

         public string getError()

         {

             return "Foo";

         }

    }

    public class B

    {

        public string getError()

        {

            return "Bar";

        }

    }

}

​

namespace InternalClasses

{

​

    public class ErrorContainer

    {

        protected string _error = null;

        public string getError()

        {

            return _error;

        }

        public override string ToString()

        {

            return getError();

        }

        static public implicit operator ErrorContainer(ExternalClasses.A a)

        {

            var e = new ErrorContainer();

            e._error = a.getError();

            return e;

        }

        static public implicit operator ErrorContainer(ExternalClasses.B b)

        {

            var e = new ErrorContainer();

            e._error = b.getError();

            return e;

        }

​

    }

    public class Program

    {

        public static void PrintError(ErrorContainer e)

        {

            Console.WriteLine(e);

        }

        public static void PrintError(ExternalClasses.A a)

        {

            Console.WriteLine(a.getError());

        }

        public static void PrintError(ExternalClasses.B b)

        {

            Console.WriteLine(b.getError());

        }

        public static void Main()

        {

            var a = new ExternalClasses.A();

            PrintError(a);

​

            var b = new ExternalClasses.B();

            PrintError(b);

        }

    }

}