CSharp: The single-responsibility principle (SRP) in donet core 6

Single Responsibility Principle SOLID Design Patterns
SOLID is an acronym for five principles of architecture.
S – Single Responsibility Principle
O – Open Close Principle
L – Liskov Substitution Principle
I –Interface Segregation Principle
D – Dependency Inversion Principle

 

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namespace SRP;   /// <summary> /// 书,geovindu /// </summary> public class Book {     /// <summary>     /// ID     /// </summary>     public int Id { get; set; }       /// <summary>     ///书的标题，书名     /// </summary>     public string? Title { get; set; } }   /// <summary> /// 书店 /// </summary> public class BookStore {       /// <summary>     ///     /// </summary>     private static int _lastId = 0;     /// <summary>     ///     /// </summary>     private static List<Book> _books;       /// <summary>     ///     /// </summary>     public static int NextId => ++_lastId;     /// <summary>     ///     /// </summary>     static BookStore()     {         _books = new List<Book>                 {                     new Book                     {                         Id = NextId,                         Title = "一些很酷的电脑书"                     }                 };     }     /// <summary>     /// 书列表     /// </summary>     public IEnumerable<Book> Books => _books;     /// <summary>     /// 保存     /// </summary>     /// <param name="book"></param>     public void Save(Book book)     {         // Create the book when it does not exist,         // otherwise, find its index and replace it         // by the specified book.         if (_books.Any(x => x.Id == book.Id))         {             var index = _books.FindIndex(x => x.Id == book.Id);             _books[index] = book;         }         else         {             _books.Add(book);         }     }     /// <summary>     /// 加载指定ID的书     /// </summary>     /// <param name="bookId"></param>     /// <returns></returns>     public Book? Load(int bookId)     {         return _books.FirstOrDefault(x => x.Id == bookId);     } } /// <summary> /// 出版社 /// </summary> public class BookPresenter {     /// <summary>     /// 显示书     /// </summary>     /// <param name="book"></param>     public void Display(Book book)     {         Console.WriteLine($"书名: {book.Title} ({book.Id})");     } }

　　

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/// <summary> /// /// </summary> public class Program {       /// <summary>     ///     /// </summary>     private static readonly BookStore _bookStore = new();     /// <summary>     ///     /// </summary>     private static readonly BookPresenter _bookPresenter = new();     /// <summary>     ///     /// </summary>     /// <param name="args"></param>     public static void Main(string[] args)     {         var run = true;         do         {             Console.Clear();             Console.WriteLine("请选择:");             Console.WriteLine("1: 获取并显示图书id 1");             Console.WriteLine("2: 找不到书");             Console.WriteLine("3: 书是不存在的");             Console.WriteLine("4: 创建一个无序的账簿");             Console.WriteLine("5: 把书陈列在别的地方");             Console.WriteLine("6: 创建一本书");             Console.WriteLine("7: 列出所有书");             //...             Console.WriteLine("0: 退出");               var input = Console.ReadLine();             Console.Clear();             try             {                 switch (input)                 {                     case "1":                         FetchAndDisplayBook();                         break;                     case "2":                         FailToFetchBook();                         break;                     case "3":                         BookDoesNotExist();                         break;                     case "4":                         CreateOutOfOrderBook();                         break;                     case "5":                         DisplayTheBookSomewhereElse();                         break;                     case "6":                         CreateBook();                         break;                     case "7":                         ListAllBooks();                         break;                     case "0":                         run = false;                         break;                     default:                         Console.WriteLine("无效的选择!");                         break;                 }                 Console.WriteLine("按回车键返回主菜单.");                 Console.ReadLine();             }             catch (Exception ex)             {                 Console.WriteLine("出现以下异常，请按回车继续:");                 Console.WriteLine(ex);                 Console.ReadLine();             }         } while (run);     }     /// <summary>     ///     /// </summary>     private static void FetchAndDisplayBook()     {         var book = _bookStore.Load(1);         _bookPresenter.Display(book!);     }     /// <summary>     ///     /// </summary>     private static void FailToFetchBook()     {         // This cannot happen anymore, this has been fixed automatically.     }     /// <summary>     ///     /// </summary>     private static void BookDoesNotExist()     {         var book = _bookStore.Load(999);         if (book == null)         {             // Book does not exist         }     }     /// <summary>     ///     /// </summary>     private static void CreateOutOfOrderBook()     {         var book = new Book         {             Id = 4, // this value is not enforced by anything and will be overriden at some point.             Title = "有些是坏的书"         };         _bookStore.Save(book);         _bookPresenter.Display(book);     }     /// <summary>     ///     /// </summary>     private static void DisplayTheBookSomewhereElse()     {         Console.WriteLine("这现在是可能的，但我们需要一个新的出版人; 还不是100 % !");     }       /// <summary>     ///     /// </summary>     private static void CreateBook()     {         Console.Clear();         Console.WriteLine("请输入书名: ");         var title = Console.ReadLine();         var book = new Book { Id = BookStore.NextId, Title = title };         _bookStore.Save(book);     }     /// <summary>     ///     /// </summary>     private static void ListAllBooks()     {         foreach (var book in _bookStore.Books)         {             _bookPresenter.Display(book);         }     }

　　

输出：

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请选择: 1: 获取并显示图书id 1 2: 找不到书 3: 书是不存在的 4: 创建一个无序的账簿 5: 把书陈列在别的地方 6: 创建一本书 7: 列出所有书 0: 退出     书名: 一些很酷的电脑书 (1) 书名: geovindu (2) 书名: 涂聚文 (3) 按回车键返回主菜单.