CSharp: null object Pattern in donet 6

 

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/// <summary>     /// 空对象模式 null object Pattern     ///     /// </summary>     public abstract class Application     {           /// <summary>         ///         /// </summary>         private static readonly NullApplication NullApplication = new NullApplication();         /// <summary>         ///         /// </summary>         /// <param name="processId"></param>         public Application(Guid processId)         {             ProcessId = processId;         }         /// <summary>         ///         /// </summary>         public static NullApplication Default         {             get             {                 return NullApplication;             }         }         /// <summary>         ///         /// </summary>         public abstract string Name { get; }         /// <summary>         ///         /// </summary>         public Guid ProcessId { get; }         /// <summary>         ///         /// </summary>         public virtual void Open()         {             Console.WriteLine($"应用程序 {Name} 已经打开.");         }         /// <summary>         ///         /// </summary>         public virtual void Close()         {             Console.WriteLine($"应用程序 {Name} 已经关闭.");         }     }           /// <summary>     /// 空对象模式 null object Pattern     /// </summary>     public class NullApplication : Application     {           /// <summary>         ///         /// </summary>         public NullApplication()             : base(Guid.Empty)         {         }         /// <summary>         ///         /// </summary>         public override string Name => string.Empty;         /// <summary>         ///         /// </summary>         public override void Open()         {         }         /// <summary>         ///         /// </summary>         public override void Close()         {         }     }         /// <summary>     ///     /// </summary>     public class Gmail : Application     {           /// <summary>         ///         /// </summary>         /// <param name="processId"></param>         public Gmail(Guid processId)             : base(processId)         {         }         /// <summary>         ///         /// </summary>         public override string Name => "Gmail";     }      /// <summary>     ///     /// </summary>     public class SubwaySurfers : Application     {           /// <summary>         ///         /// </summary>         /// <param name="processId"></param>         public SubwaySurfers(Guid processId)             : base(processId)         {         }         /// <summary>         ///         /// </summary>         public override string Name => "Subway Surfers";     }   using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using Geovin.Du.DuNullObject.Applications.Common;     namespace Geovin.Du.DuNullObject.Applications {       /// <summary>     ///     /// </summary>     public class GeovinDu : Application     {           /// <summary>         ///         /// </summary>         /// <param name="processId"></param>         public GeovinDu(Guid processId)             : base(processId)         {         }         /// <summary>         ///         /// </summary>         public override string Name => "GeovinDu";     } }      /// <summary>     ///     /// </summary>     public class ApplicationRepository     {           /// <summary>         ///         /// </summary>         private readonly Dictionary<Guid, Application> _installedApplications;             /// <summary>         ///         /// </summary>         public ApplicationRepository()         {             var gmailProcessId = new Guid("6a3852ab-0973-4d1b-82d8-edd131c5f0a9");             var subwaySurfersProcessId = new Guid("c8bc60c6-f1d2-484f-91ee-a6e6dec9e782");             var geovinduProcessId = new Guid("2b8ba9a3-4f83-4f86-96a8-94daf79fa4bd");               _installedApplications = new Dictionary<Guid, Application>             {                 { gmailProcessId, new Gmail(gmailProcessId) },                 { subwaySurfersProcessId, new SubwaySurfers(subwaySurfersProcessId) },                 { geovinduProcessId, new GeovinDu(youtubeProcessId) },             };         }         /// <summary>         ///         /// </summary>         /// <param name="processId"></param>         /// <returns></returns>         public Application Find(Guid processId)         {             if (_installedApplications.TryGetValue(processId, out Application application))             {                 return application;             }               return Application.Default;         }     }       /// <summary>     /// 空对象模式 null object Pattern     /// geovindu,Geovin Du,涂聚文     /// </summary>     public static class SmartphoneApplicationExecutor     {           /// <summary>         ///         /// </summary>         public static void Execute()         {               ConsoleExtension.WriteSeparator("小手机应用程序 Demo");               var applicationRepository = new ApplicationRepository();               var validProcessId = new Guid("6a3852ab-0973-4d1b-82d8-edd131c5f0a9");             var invalidProcessId = Guid.Empty;               var gmail = applicationRepository.Find(validProcessId);             gmail.Open();             gmail.Close();               // Null exception won't be thrown if an application with the specified process ID can't be found.             // In that case, default (NULL) object will be returned.             var geovindu = applicationRepository.Find(invalidProcessId);             geovindu.Open();             geovindu.Close();         }     }

　　

调用：

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Console.WriteLine("Hello, Geovin Du! 学习 .net 6 "); //Geovin.Du.DuEmail.EmailExecutor.Execute(); //Geovin.Du.DuStock.StockExecutor.Execute(); // Geovin.Du.DuShoppingCart.ShoppingCartExecutor.Execute(); Geovin.Du.DuNullObject.SmartphoneApplicationExecutor.Execute();

　　

输出：

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Hello, Geovin Du! 学习 .net 6   小手机应用程序 Demo -------------------------------------------------- 应用程序 Gmail 已经打开. 应用程序 Gmail 已经关闭.

　　

 

 

 

 

 

 

 

 

 

 

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