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using System;
 
public class Test
{
    public static void Main()
    {
        Zoo zoo = new Zoo();
        CountingVisitor v = new CountingVisitor();
        zoo.Accept(v);
        v.Summary();
    }
 
    interface AnimalVisitor
    {
        void Visit(Animal animal);
    }
 
    interface Animal {}
 
    class Zoo
    {
        Animal[] animals = new Animal[]
        {
            new Giraffe(),
            new Zebra(),
            new Lion(),
            new Penguin()
        };
 
        public void Accept(AnimalVisitor visitor)
        {
            foreach (var a in animals)
                visitor.Visit(a);
        }
    }
 
    class Giraffe : Animal {}
    class Zebra : Animal {}    
    class Lion : Animal {}
    class Penguin : Animal {}
 
    class CountingVisitor : AnimalVisitor
    {
        int numberOfMammals;
        int numberOfBirds;
        int numberOfMonochromeAnimals;
        public void Summary()
        {
            Console.WriteLine("Discovered {0} mammals, {1} birds", numberOfMammals, numberOfBirds);
            Console.WriteLine("Total {0} monochrome animals", numberOfMonochromeAnimals);
        }
        public void Visit(Animal animal)
        {
            VisitImpl((dynamic)animal);
        }
        void VisitImpl(Giraffe giraffe)
        {
            numberOfMammals++;
        }
        void VisitImpl(Zebra zebra)
        {
            numberOfMammals++;
            numberOfMonochromeAnimals++;
        }
        void VisitImpl(Lion lion)
        {
            numberOfMammals++;
            Console.WriteLine("Lions are NOT scary");
        }
        void VisitImpl(Penguin penguin)
        {
            numberOfBirds++;
            numberOfMonochromeAnimals++;
        }
    }
}

prog.cs(54,24): error CS1980: Dynamic keyword requires `System.Runtime.CompilerServices.DynamicAttribute' to be defined. Are you missing System.Core.dll assembly reference?
prog.cs(54,13): error CS0518: The predefined type `Microsoft.CSharp.RuntimeBinder.Binder' is not defined or imported
prog.cs(54,13): error CS0518: The predefined type `System.Runtime.CompilerServices.CallSite' is not defined or imported
prog.cs(54,13): error CS0518: The predefined type `System.Runtime.CompilerServices.CallSite' is not defined or imported
prog.cs(54,13): error CS1969: Dynamic operation cannot be compiled without `Microsoft.CSharp.dll' assembly reference
Compilation failed: 5 error(s), 0 warnings

Standard output is empty