1.3 Basics: interfaces, C#

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//1.3 Interfaces

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //interface is a declaration of a contract, i.e. if interface does A()
            //and I give you an object that implements this interface
            //then this object must also do A()
            
            //This way you can write code that takes not concrete types, but interfaces
            //And then supply it any type that satisfies this interface
            
            ConcertArena concert = new ConcertArena();
            concert.PerformConcert(new List<ISinging>(){new RobbieWilliams(), new SnoopLion()});
            
            //concert.PerformConcert(new List<ISinging>(){new JamesBond()}); //JamesBond can't sing
            
        }
    }
    
    public class ConcertArena
    {
        public void PerformConcert(List<ISinging> artists)
        {
            foreach(ISinging a in artists)
            {
                a.Sing();
            }
        }
    }
    public interface ISinging
    {
        void Sing();
    }
    
    public class RobbieWilliams : ISinging
    {
        public void Sing()
        {
            Console.WriteLine("♪♪♪  robbie williams sings ♪♪♪");
        }
    }
    
    public class SnoopLion : ISinging
    {
        public void Sing()
        {
            Console.WriteLine("♪♪♪  snoop lion sings ♪♪♪");
        }
    }
    
    public class JamesBond
    {
        public void Sing()
        {
            Console.WriteLine("Daniel Craig tries to sing, but well ...");
        }
    }
}

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