2024013293_宋钧亭_笃实42_4异步与多线程作业

homework.cs

@@ -5,33 +5,54 @@
 
 public class Book
 {
-    public string Title { get; set; }
-    public decimal Price { get; set; }
-    public int Inventory { get; set; }
+    public string Title { get; set; }  // 书籍标题
+    public decimal Price { get; set; }  // 书籍价格
+    public int Inventory { get; set; }  // 书籍库存
 }
 
 public class Database
 {
-    private readonly List<Book> _books = new List<Book>();
-    private readonly object _lock = new object();
+    private readonly List<Book> _books = new List<Book>();  // 书籍列表
+    private readonly object _lock = new object();  // 用于线程同步的锁对象
 
     public Database()
     {
+        // 初始化书籍数据
         _books.Add(new Book { Title = "C#入门", Price = 39.9m, Inventory = 10 });
         _books.Add(new Book { Title = "异步编程", Price = 59.9m, Inventory = 5 });
     }
 
     public Task<List<Book>> GetBooksAsync()
     {
-        return Task.FromResult(_books);
+        return Task.FromResult(_books);  // 同步方法包装为异步返回
     }
 
     public async Task UpdateInventoryAsync(string title, int quantity)
     {
-        await Task.Delay(100); // 模拟网络延迟
+        await Task.Delay(100);  // 模拟网络延迟
 
         // TODO: 使用 lock 语句保证线程安全
         // 提示：在 lock 块中查找书籍并更新库存，若库存不足则输出提示
+        lock (_lock)
+        {
+            var book = _books.Find(b => b.Title == title);
+            if (book != null)
+            {
+                if (book.Inventory >= quantity)
+                {
+                    book.Inventory -= quantity;
+                    Console.WriteLine($"购买 {title} {quantity} 本成功");
+                }
+                else
+                {
+                    Console.WriteLine($"库存不足，无法购买 {title}");
+                }
+            }
+            else
+            {
+                Console.WriteLine($"未找到书籍 {title}");
+            }
+        }
     }
 }
 
@@ -42,6 +63,7 @@ public class BookStore
     // TODO: 实现异步购书方法CheckoutAsync，调用 UpdateInventoryAsync
     public async Task CheckoutAsync(string bookTitle, int quantity)
     {
+        await _db.UpdateInventoryAsync(bookTitle, quantity);
     }
 
     public async Task SimulateMultipleUsers()
@@ -59,9 +81,14 @@ public async Task SimulateMultipleUsers()
         // 提示：创建多个 Task 调用 CheckoutAsync，并传入不同书名和数量
         var tasks = new List<Task>
         {
-
+            CheckoutAsync("C#入门", 2),
+            CheckoutAsync("C#入门", 3),
+            CheckoutAsync("异步编程", 1),
+            CheckoutAsync("异步编程", 2),
+            CheckoutAsync("异步编程", 3)
         };
 
+        await Task.WhenAll(tasks);
 
         Console.WriteLine("\n购买后库存：");
         books = await _db.GetBooksAsync();