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index 0000000..0e90aa2
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diff --git a/.vs/Async-and-Multi_thread/FileContentIndex/62af47c7-bf26-49bc-b556-52b1d0e8c2d5.vsidx b/.vs/Async-and-Multi_thread/FileContentIndex/62af47c7-bf26-49bc-b556-52b1d0e8c2d5.vsidx
new file mode 100644
index 0000000..aa5f10f
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diff --git a/.vs/Async-and-Multi_thread/v17/.wsuo b/.vs/Async-and-Multi_thread/v17/.wsuo
new file mode 100644
index 0000000..187e2fc
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diff --git a/.vs/Async-and-Multi_thread/v17/DocumentLayout.backup.json b/.vs/Async-and-Multi_thread/v17/DocumentLayout.backup.json
new file mode 100644
index 0000000..9f688c4
--- /dev/null
+++ b/.vs/Async-and-Multi_thread/v17/DocumentLayout.backup.json
@@ -0,0 +1,37 @@
+{
+  "Version": 1,
+  "WorkspaceRootPath": "C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\",
+  "Documents": [
+    {
+      "AbsoluteMoniker": "D:0:0:{A2FE74E1-B743-11D0-AE1A-00A0C90FFFC3}|\u003CMiscFiles\u003E|C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\homework.cs||{A6C744A8-0E4A-4FC6-886A-064283054674}",
+      "RelativeMoniker": "D:0:0:{A2FE74E1-B743-11D0-AE1A-00A0C90FFFC3}|\u003CMiscFiles\u003E|solutionrelative:homework.cs||{A6C744A8-0E4A-4FC6-886A-064283054674}"
+    }
+  ],
+  "DocumentGroupContainers": [
+    {
+      "Orientation": 0,
+      "VerticalTabListWidth": 256,
+      "DocumentGroups": [
+        {
+          "DockedWidth": 200,
+          "SelectedChildIndex": 0,
+          "Children": [
+            {
+              "$type": "Document",
+              "DocumentIndex": 0,
+              "Title": "homework.cs",
+              "DocumentMoniker": "C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\homework.cs",
+              "RelativeDocumentMoniker": "homework.cs",
+              "ToolTip": "C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\homework.cs",
+              "RelativeToolTip": "homework.cs",
+              "ViewState": "AgIAAAAAAAAAAAAAAAAAABcAAAArAAAAAAAAAA==",
+              "Icon": "ae27a6b0-e345-4288-96df-5eaf394ee369.000738|",
+              "WhenOpened": "2025-08-28T03:16:16.226Z",
+              "EditorCaption": ""
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
\ No newline at end of file
diff --git a/.vs/Async-and-Multi_thread/v17/DocumentLayout.json b/.vs/Async-and-Multi_thread/v17/DocumentLayout.json
new file mode 100644
index 0000000..9f688c4
--- /dev/null
+++ b/.vs/Async-and-Multi_thread/v17/DocumentLayout.json
@@ -0,0 +1,37 @@
+{
+  "Version": 1,
+  "WorkspaceRootPath": "C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\",
+  "Documents": [
+    {
+      "AbsoluteMoniker": "D:0:0:{A2FE74E1-B743-11D0-AE1A-00A0C90FFFC3}|\u003CMiscFiles\u003E|C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\homework.cs||{A6C744A8-0E4A-4FC6-886A-064283054674}",
+      "RelativeMoniker": "D:0:0:{A2FE74E1-B743-11D0-AE1A-00A0C90FFFC3}|\u003CMiscFiles\u003E|solutionrelative:homework.cs||{A6C744A8-0E4A-4FC6-886A-064283054674}"
+    }
+  ],
+  "DocumentGroupContainers": [
+    {
+      "Orientation": 0,
+      "VerticalTabListWidth": 256,
+      "DocumentGroups": [
+        {
+          "DockedWidth": 200,
+          "SelectedChildIndex": 0,
+          "Children": [
+            {
+              "$type": "Document",
+              "DocumentIndex": 0,
+              "Title": "homework.cs",
+              "DocumentMoniker": "C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\homework.cs",
+              "RelativeDocumentMoniker": "homework.cs",
+              "ToolTip": "C:\\Users\\32084\\Desktop\\Async-and-Multi_thread\\homework.cs",
+              "RelativeToolTip": "homework.cs",
+              "ViewState": "AgIAAAAAAAAAAAAAAAAAABcAAAArAAAAAAAAAA==",
+              "Icon": "ae27a6b0-e345-4288-96df-5eaf394ee369.000738|",
+              "WhenOpened": "2025-08-28T03:16:16.226Z",
+              "EditorCaption": ""
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
\ No newline at end of file
diff --git a/.vs/ProjectSettings.json b/.vs/ProjectSettings.json
new file mode 100644
index 0000000..f8b4888
--- /dev/null
+++ b/.vs/ProjectSettings.json
@@ -0,0 +1,3 @@
+{
+  "CurrentProjectSetting": null
+}
\ No newline at end of file
diff --git a/.vs/VSWorkspaceState.json b/.vs/VSWorkspaceState.json
new file mode 100644
index 0000000..d282b3b
--- /dev/null
+++ b/.vs/VSWorkspaceState.json
@@ -0,0 +1,7 @@
+{
+  "ExpandedNodes": [
+    ""
+  ],
+  "SelectedNode": "\\README.md",
+  "PreviewInSolutionExplorer": false
+}
\ No newline at end of file
diff --git a/.vs/slnx.sqlite b/.vs/slnx.sqlite
new file mode 100644
index 0000000..6c3dc60
Binary files /dev/null and b/.vs/slnx.sqlite differ
diff --git a/homework.cs b/homework.cs
index 91a7fc0..980d6d4 100644
--- a/homework.cs
+++ b/homework.cs
@@ -29,7 +29,25 @@ public Task<List<Book>> GetBooksAsync()
     public async Task UpdateInventoryAsync(string title, int quantity)
     {
         await Task.Delay(100); // 模拟网络延迟
-
+        lock (_lock) {
+            var book = _books.Find(b => b.Title == title);
+            if (book != null)
+            {
+                if (book.Inventory >= quantity)
+                {
+                    book.Inventory -= quantity;
+                    Console.WriteLine($"成功购买 {quantity} 本《{title}》，剩余库存：{book.Inventory} 本");
+                }
+                else
+                {
+                    Console.WriteLine($"库存不足，无法购买 {quantity} 本《{title}》，当前库存：{book.Inventory} 本");
+                }
+            }
+            else
+            {
+                Console.WriteLine($"书籍《{title}》不存在");
+            }
+        }
         // 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
     }
@@ -42,6 +60,7 @@ 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()
@@ -59,10 +78,14 @@ 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();
         foreach (var book in books)