CSharp: Observer Pattern in donet core 3

 

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/// <summary>     ///观察者模式 Observer Pattern  亦称： 事件订阅者、监听者、Event-Subscriber、Listener、Observe     /// geovindu,Geovin Du eidt     ///     /// </summary>     interface IObserver     {         /// <summary>         ///         /// </summary>         /// <param name="celeb">对象</param>         void Update(ICelebrity celeb);     }       /// <summary>     /// /     /// </summary>     class ObserverType1 : IObserver     {           /// <summary>         /// 名称         /// </summary>         string nameOfObserver;           /// <summary>         /// /         /// </summary>         /// <param name="name">输入名称</param>         public ObserverType1(String name)         {             this.nameOfObserver = name;         }         /// <summary>         /// 更新         /// </summary>         /// <param name="celeb"></param>         public void Update(ICelebrity celeb)         {             Console.WriteLine($"{nameOfObserver} has received（接收） an alert from {celeb.Name}.Updated value is（更新标志值）: {celeb.Flag}");         }       }       /// <summary>     ///     /// </summary>     class ObserverType2 : IObserver     {           /// <summary>         /// 名称         /// </summary>         string nameOfObserver;         /// <summary>         ///         /// </summary>         /// <param name="name">输入名称</param>         public ObserverType2(String name)         {             this.nameOfObserver = name;         }         /// <summary>         /// 更新         /// </summary>         /// <param name="celeb"></param>         public void Update(ICelebrity celeb)         {             Console.WriteLine($"{nameOfObserver} notified（通知）.Inside {celeb.Name}, the updated value is: {celeb.Flag}");         }     }     /// <summary>     ///     /// </summary>     interface ICelebrity     {         /// <summary>         /// Name of Subject         /// 名称         /// </summary>         string Name { get; }         /// <summary>         /// 标记         /// </summary>         int Flag { get; set; }         /// <summary>         /// To register         /// 注册         /// </summary>         /// <param name="o"></param>         void Register(IObserver o);         /// <summary>         /// To Unregister         /// 取消注册         /// </summary>         /// <param name="o"></param>         void Unregister(IObserver o);         ///<summary>         ///To notify registered users               ///注册用户         /// </summary>         void NotifyRegisteredUsers();       }       /// <summary>     ///     /// </summary>     class Celebrity : ICelebrity     {           /// <summary>         /// 对像数列         /// </summary>         List<IObserver> observerList = new List<IObserver>();         /// <summary>         /// 标记         /// </summary>         private int flag;           /// <summary>         /// 标记         /// </summary>         public int Flag         {             get             {                 return flag;             }             set             {                 flag = value;                 //Flag value changed. So notify observer(s).                 NotifyRegisteredUsers();             }         }           /// <summary>         ///         /// </summary>         private string name;         /// <summary>         ///         /// </summary>         /// <param name="name">输入名称</param>         public Celebrity(string name)         {             this.name = name;         }         //public string Name         //{         //    get         //    {         //        return name;         //    }                   //}         //Or, simply use expression bodied         //properties(C#6.0 onwards)         /// <summary>         ///         /// </summary>         public string Name => name;           /// <summary>         /// To register an observer.         /// </summary>         /// <param name="anObserver">对象</param>         public void Register(IObserver anObserver)         {             observerList.Add(anObserver);         }                 /// <summary>         /// To unregister an observer.         /// </summary>         /// <param name="anObserver"></param>         public void Unregister(IObserver anObserver)         {             observerList.Remove(anObserver);         }              /// <summary>         /// Notify all registered observers.         /// </summary>         public void NotifyRegisteredUsers()         {             foreach (IObserver observer in observerList)             {                 observer.Update(this);             }         }     }

　　

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/// <summary>   ///观察者模式 Observer Pattern  亦称： 事件订阅者、监听者、Event-Subscriber、Listener、Observe   /// geovindu,Geovin Du eidt   /// 产品   /// </summary>   public class Product : INotifyPropertyChanged   {         /// <summary>       /// 名特       /// </summary>       private string name;       /// <summary>       /// 名称       /// </summary>       public string Name       {           get => name;           set           {               if (value == name) return; // critical               name = value;               OnPropertyChanged();           }       }       /// <summary>       ///       /// </summary>       public event PropertyChangedEventHandler PropertyChanged;       /// <summary>       ///       /// </summary>       /// <param name="propertyName"></param>       [NotifyPropertyChangedInvocator]       protected virtual void OnPropertyChanged(         [CallerMemberName] string propertyName = null)       {           PropertyChanged?.Invoke(this,             new PropertyChangedEventArgs(propertyName));       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public override string ToString()       {           return $"产品名称: {Name}";       }   }   /// <summary>   /// 窗口   /// </summary>   public class Window : INotifyPropertyChanged   {       /// <summary>       ///       /// </summary>       private string productName;       /// <summary>       ///       /// </summary>       public string ProductName       {           get => productName;           set           {               if (value == productName) return; // critical               productName = value;               OnPropertyChanged();           }       }       /// <summary>       ///       /// </summary>       public event PropertyChangedEventHandler PropertyChanged;       /// <summary>       ///       /// </summary>       /// <param name="propertyName"></param>       [NotifyPropertyChangedInvocator]       protected virtual void OnPropertyChanged(         [CallerMemberName] string propertyName = null)       {           PropertyChanged?.Invoke(this,             new PropertyChangedEventArgs(propertyName));       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public override string ToString()       {           return $"窗口: {ProductName}";       }   }   /// <summary>   ///   /// </summary>   public sealed class BidirectionalBinding : IDisposable   {         /// <summary>       ///       /// </summary>       private bool disposed;       /// <summary>       ///       /// </summary>       /// <param name="first"></param>       /// <param name="firstProperty"></param>       /// <param name="second"></param>       /// <param name="secondProperty"></param>       public BidirectionalBinding(         INotifyPropertyChanged first,         Expression<Func<object>> firstProperty,         INotifyPropertyChanged second,         Expression<Func<object>> secondProperty)       {           if (firstProperty.Body is MemberExpression firstExpr               && secondProperty.Body is MemberExpression secondExpr)           {               if (firstExpr.Member is PropertyInfo firstProp                   && secondExpr.Member is PropertyInfo secondProp)               {                   first.PropertyChanged += (sender, args) =>                   {                       if (!disposed)                       {                           secondProp.SetValue(second, firstProp.GetValue(first));                       }                   };                   second.PropertyChanged += (sender, args) =>                   {                       if (!disposed)                       {                           firstProp.SetValue(first, secondProp.GetValue(second));                       }                   };               }           }       }       /// <summary>       ///       /// </summary>       public void Dispose()       {           disposed = true;       }   }

　　

调用：

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//观察者模式 Observer Pattern            Console.WriteLine("***观察者模式 Observer Pattern Demonstration.***\n");            //We have 4 observers-2 of them are ObserverType1, 1  is of ObserverType2            IObserver myObserver1 = new ObserverType1("刘二");            IObserver myObserver2 = new ObserverType1("刘三");            IObserver myObserver3 = new ObserverType2("刘四");            IObserver myObserver4 = new ObserverType2("刘五");            Console.WriteLine("Working with first celebrity now.");            ICelebrity celebrity = new Celebrity("Celebrity名人-1组");            //Registering the observers-Roy,Kevin,Bose            celebrity.Register(myObserver1);            celebrity.Register(myObserver2);            celebrity.Register(myObserver3);            Console.WriteLine(" Celebrity-1 is setting Flag 设置标志 = 5.");            celebrity.Flag = 5;            /*            Kevin doesn't want to get further notification.            So, unregistering the observer(Kevin)).            */            Console.WriteLine("\nCelebrity-名人1组 is removing（移除） 刘三 from the observer list now.");            celebrity.Unregister(myObserver2);                       //No notification is sent to Kevin this time. He has unregistered.            Console.WriteLine("\n Celebrity-名人1组 is setting Flag 设置标志= 50.");            celebrity.Flag = 50;            //Kevin is registering himself again            celebrity.Register(myObserver2);            Console.WriteLine("\n Celebrity-名人1组 is setting Flag 设置标志= 100.");            celebrity.Flag = 100;              Console.WriteLine("\n Working with another celebrity now.");            //Creating another celebrity            ICelebrity celebrity2 = new Celebrity("Celebrity-名人2组");            //Registering the observers-Roy and Jacklin            celebrity2.Register(myObserver1);            celebrity2.Register(myObserver4);            Console.WriteLine("\n --Celebrity-名人2组 is setting Flag value as设置标志 500.--");            celebrity2.Flag = 500;              //            var product = new Product { Name = "书" };            var window = new Window { ProductName = "书" };              // want to ensure that when product name changes            // in one component, it also changes in another              product.PropertyChanged += (sender, eventArgs) =>            {                if (eventArgs.PropertyName == "Name")                {                    Console.WriteLine("Name changed in Product");                    window.ProductName = product.Name;                    Console.WriteLine("changed 1." + product);                    Console.WriteLine("changed 1." + window);                }            };              window.PropertyChanged += (sender, eventArgs) =>            {                if (eventArgs.PropertyName == "ProductName")                {                    Console.WriteLine("Name changed in Window");                    product.Name = window.ProductName;                    Console.WriteLine("changed 2." + product);                    Console.WriteLine("changed 2." + window);                }            };              using var binding = new BidirectionalBinding(              product,              () => product.Name,              window,              () => window.ProductName);              Console.WriteLine("1."+product); //书            Console.WriteLine("2."+window);              // there is no infinite loop because of            // self-assignment guard            product.Name = "桌子";            window.ProductName = "椅子";              Console.WriteLine(product);            Console.WriteLine(window);                  Console.ReadKey();

　　

输出：

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***观察者模式 Observer Pattern Demonstration.***   Working with first celebrity now.  Celebrity-1 is setting Flag 设置标志 = 5. 刘二 has received（接收） an alert from Celebrity名人-1组.Updated value is（更新标志值）: 5 刘三 has received（接收） an alert from Celebrity名人-1组.Updated value is（更新标志值）: 5 刘四 notified（通知）.Inside Celebrity名人-1组, the updated value is: 5   Celebrity-名人1组 is removing（移除） 刘三 from the observer list now.    Celebrity-名人1组 is setting Flag 设置标志= 50. 刘二 has received（接收） an alert from Celebrity名人-1组.Updated value is（更新标志值）: 50 刘四 notified（通知）.Inside Celebrity名人-1组, the updated value is: 50    Celebrity-名人1组 is setting Flag 设置标志= 100. 刘二 has received（接收） an alert from Celebrity名人-1组.Updated value is（更新标志值）: 100 刘四 notified（通知）.Inside Celebrity名人-1组, the updated value is: 100 刘三 has received（接收） an alert from Celebrity名人-1组.Updated value is（更新标志值）: 100    Working with another celebrity now.    --Celebrity-名人2组 is setting Flag value as设置标志 500.-- 刘二 has received（接收） an alert from Celebrity-名人2组.Updated value is（更新标志值）: 500 刘五 notified（通知）.Inside Celebrity-名人2组, the updated value is: 500 1.产品名称: 书 2.窗口: 书 Name changed in Product Name changed in Window changed 2.产品名称: 桌子 changed 2.窗口: 桌子 changed 1.产品名称: 桌子 changed 1.窗口: 桌子 Name changed in Window Name changed in Product changed 1.产品名称: 椅子 changed 1.窗口: 椅子 changed 2.产品名称: 椅子 changed 2.窗口: 椅子 产品名称: 椅子 窗口: 椅子