class Program
    {
        /// <summary>
        /// 抽象圖形定義--相當(dāng)于“抽象節(jié)點(diǎn)角色”
        /// </summary>
        public abstract class Shape
        {
            //畫(huà)圖形
            public abstract void Draw();
            //外界注入具體訪(fǎng)問(wèn)者
            public abstract void Accept(ShapeVisitor visitor);
        }

        /// <summary>
        /// 矩形--相當(dāng)于“具體節(jié)點(diǎn)角色”
        /// </summary>
        public sealed class Rectangle : Shape
        {
            public override void Draw()
            {
                Console.WriteLine("矩形我已經(jīng)畫(huà)好了。");
            }

            public override void Accept(ShapeVisitor visitor)
            {
                visitor.Visit(this);
            }
        }

        /// <summary>
        /// 圓形--相當(dāng)于“具體節(jié)點(diǎn)角色”
        /// </summary>
        public sealed class Circle : Shape
        {
            public override void Draw()
            {
                Console.WriteLine("圓形我已經(jīng)畫(huà)好了。");
            }

            public override void Accept(ShapeVisitor visitor)
            {
                visitor.Visit(this);
            }
        }

        /// <summary>
        /// 直線(xiàn)--相當(dāng)于“具體節(jié)點(diǎn)角色”
        /// </summary>
        public sealed class Line : Shape
        {
            public override void Draw()
            {
                Console.WriteLine("直線(xiàn)我已經(jīng)畫(huà)好了。");
            }

            public override void Accept(ShapeVisitor visitor)
            {
                visitor.Visit(this);
            }
        }

        /// <summary>
        /// 抽象訪(fǎng)問(wèn)者
        /// </summary>
        public abstract class ShapeVisitor
        {
            public abstract void Visit(Rectangle shape);

            public abstract void Visit(Circle shape);

            public abstract void Visit(Line shape);

            //這里有一點(diǎn)要說(shuō)：Visit方法的參數(shù)可以寫(xiě)成Shape嗎？就是這樣Visit(Shape shape)。
            //答案是可以，但是ShapeVisitor子類(lèi)的Visit方法就需要判斷當(dāng)前的Shape是什么類(lèi)型？是Rectangle類(lèi)型？還是Circle類(lèi)型？或者是Line類(lèi)型？
        }

        /// <summary>
        /// 具體訪(fǎng)問(wèn)者
        /// </summary>
        public sealed class CustomVisitor : ShapeVisitor
        {
            //針對(duì)Rectangle對(duì)象
            public override void Visit(Rectangle shape)
            {
                Console.WriteLine("針對(duì)Rectangle新的操作。");
            }
            //針對(duì)Circle對(duì)象
            public override void Visit(Circle shape)
            {
                Console.WriteLine("針對(duì)Circle新的操作。");
            }
            //針對(duì)Line對(duì)象
            public override void Visit(Line shape)
            {
                Console.WriteLine("針對(duì)Line新的操作。");
            }
        }

        /// <summary>
        /// 結(jié)構(gòu)對(duì)象角色
        /// </summary>
        internal class AppStructure
        {
            private readonly ShapeVisitor _visitor;

            public AppStructure(ShapeVisitor visitor)
            {
                _visitor = visitor;
            }

            public void Process(Shape shape)
            {
                shape.Accept(_visitor);
            }
        }

        static void Main(string[] args)
        {
            #region 訪(fǎng)問(wèn)者模式(第一個(gè)實(shí)例)
            ShapeVisitor visitor = new CustomVisitor();
            AppStructure app = new AppStructure(visitor);

            Shape shape = new Rectangle();
            shape.Draw();       //執(zhí)行自己的操作
            app.Process(shape); //執(zhí)行新的操作


            shape = new Circle();
            shape.Draw();       //執(zhí)行自己的操作
            app.Process(shape); //執(zhí)行新的操作


            shape = new Line();
            shape.Draw();       //執(zhí)行自己的操作
            app.Process(shape); //執(zhí)行新的操作

            Console.ReadLine();
            #endregion
        }
    }

    class Program
    {
        /// <summary>
        /// 抽象訪(fǎng)問(wèn)者角色
        /// </summary>
        public abstract class Visitor
        {
            public abstract void PutTelevision(Television tv);

            public abstract void PutComputer(Computer comp);
        }

        /// <summary>
        /// 具體訪(fǎng)問(wèn)者角色
        /// </summary>
        public sealed class SizeVisitor : Visitor
        {
            public override void PutTelevision(Television tv)
            {
                Console.WriteLine("按電視大小{0}排放。", tv.Size);
            }

            public override void PutComputer(Computer comp)
            {
                Console.WriteLine("按電腦大小{0}排放。", comp.Size);
            }
        }

        /// <summary>
        /// 具體訪(fǎng)問(wèn)者角色
        /// </summary>
        public sealed class StateVisitor : Visitor
        {
            public override void PutTelevision(Television tv)
            {
                Console.WriteLine("按電視新舊值{0}排放", tv.State);
            }

            public override void PutComputer(Computer comp)
            {
                Console.WriteLine("按電腦新舊值{0}排放", comp.State);
            }
        }

        /// <summary>
        /// 抽象節(jié)點(diǎn)角色
        /// </summary>
        public abstract class Goods
        {
            public abstract void Operate(Visitor visitor);
            public int Size { get; set; }
            public int State { get; set; }
        }

        /// <summary>
        /// 具體節(jié)點(diǎn)角色
        /// </summary>
        public sealed class Television : Goods
        {
            public override void Operate(Visitor visitor)
            {
                visitor.PutTelevision(this);
            }
        }

        /// <summary>
        /// 具體節(jié)點(diǎn)角色
        /// </summary>
        public sealed class Computer : Goods
        {
            public override void Operate(Visitor visitor)
            {
                visitor.PutComputer(this);
            }
        }

        /// <summary>
        /// 結(jié)構(gòu)對(duì)象角色
        /// </summary>
        public sealed class StoragePlatform
        {
            private IList<Goods> list = new List<Goods>();

            public void Attach(Goods element)
            {
                list.Add(element);
            }

            public void Detach(Goods element)
            {
                list.Remove(element);
            }

            public void Operate(Visitor visitor)
            {
                foreach (Goods g in list)
                {
                    g.Operate(visitor);
                }
            }
        }

        static void Main(string[] args)
        {
            #region 訪(fǎng)問(wèn)者模式(第二個(gè)實(shí)例)
            StoragePlatform platform = new StoragePlatform();
            platform.Attach(new Television());
            platform.Attach(new Computer());

            SizeVisitor sizeVisitor = new SizeVisitor();
            StateVisitor stateVisitor = new StateVisitor();

            platform.Operate(sizeVisitor);
            platform.Operate(stateVisitor);

            Console.Read();
            #endregion
        }
    }