doc: update docs/cs.md

docs/cs.md

@@ -1065,23 +1065,17 @@ bool hasKey2 = hashTable.ContainsKey("key2");
 string valueOfKey2 = (string)hashTable["key2"];
 ```
 
-
-
 LINQ
 --------
 
 > C#语言中的LINQ（Language-Integrated Query）是一种强大的查询语言，它提供了一种统一的编程模型，使得数据查询变得更加直观和简洁。
 
-
-
 ### FROM
 
 <!--rehype:wrap-class=col-span-3-->
 
 > 任何数据源，包括对象集合、数据库、XML等。
 
-
-
 ### WHERE
 
 <!--rehype:wrap-class=col-span-2&style=background:#e91e63;-->
@@ -1115,8 +1109,6 @@ List<string> nameList = new() { "Bob", "Echo" };
 var result4 = students.Where(student => nameList.Contains(student.Name));
 ```
 
-
-
 ### GROUPBY
 
 > 分组查询
@@ -1140,8 +1132,6 @@ var groupedByGrade = students.GroupBy(student => student.Grade);
 
 <!--rehype:className=wrap-text-->
 
-
-
 ### SELECT
 
 <!--rehype:wrap-class=col-span-2&style=background:#e91e63;-->
@@ -1163,9 +1153,9 @@ List<Student> students = new List<Student>
 
 // 使用SELECT创建一个新的匿名类，并输出为集合，一般配合Where使用
 var result1 = students.Select(student => 
-	new 
+  new 
     {
-    	student.Name,
+      student.Name,
         student.Age
     });
 
@@ -1177,8 +1167,6 @@ var result2 = students.Select(student => new StudentDto()
     });
 ```
 
-
-
 ### ORDERBY
 
 > 排序
@@ -1205,24 +1193,26 @@ var result2 = students.OrderByDescending(student => student.Age);
 
 <!--rehype:className=wrap-text-->
 
-
-
 ### JOIN
 
 <!--rehype:wrap-class=col-span-3-->
 
-> `Join`：用于执行内连接操作，它会返回两个数据源中满足连接条件的元素的交集
+- `Join`：用于执行内连接操作，它会返回两个数据源中满足连接条件的元素的交集
->
+- `GroupJoin`：用于执行左外连接（left outer join）操作，它会返回左边数据源的所有元素，以及每个元素所匹配的右边数据源的元素组成的集合。(嵌套)
-> `GroupJoin`：用于执行左外连接（left outer join）操作，它会返回左边数据源的所有元素，以及每个元素所匹配的右边数据源的元素组成的集合。(嵌套)
+
+示例数据源
 
 ```cs
-// 示例数据源
 List<Department> departments = new List<Department>
 {
     new Department { ID = 1, Name = "HR" },
     new Department { ID = 2, Name = "IT" }
 };
-// 示例数据源
+```
+
+示例数据源
+
+```cs
 List<Employee> employees = new List<Employee>
 {
     new Employee { DepartmentID = 1, Name = "Alice" },
@@ -1230,28 +1220,31 @@ List<Employee> employees = new List<Employee>
     new Employee { DepartmentID = 1, Name = "Charlie" },
     new Employee { DepartmentID = 3, Name = "David" }
 };
-
-// 使用Join，将部门和员工相结合，获取部门名称和员工名称的集合
-var joinQuery = departments.Join(employees, 
-        department => department.ID, employee => employee.DepartmentID, 
-        (department, employee) => new { Department = department.Name, Employee = employee.Name }
-    );
-
-// 使用GroupJoin，将部门和员工相结合，返回所有的部门，并返回每个部门相关联的员工集合(嵌套)
-var groupJoinQuery = departments.GroupJoin(employees, 
-        department => department.ID, employee => employee.DepartmentID, 
-        (department, employeeGroup) => new 
-            { 
-                Department = department.Name, 
-                Employees = employeeGroup.Select(e => e.Name).ToList() 
-            }
-    );
 ```
 
+使用 `Join`，将部门和员工相结合，获取部门名称和员工名称的集合
 
+```cs
+var joinQuery = departments.Join(employees, 
+    department => department.ID, employee => employee.DepartmentID, 
+    (department, employee) => new { Department = department.Name, Employee = employee.Name }
+);
+```
+
+使用 `GroupJoin`，将部门和员工相结合，返回所有的部门，并返回每个部门相关联的员工集合(嵌套)
+
+```cs
+var groupJoinQuery = departments.GroupJoin(employees, 
+    department => department.ID, employee => employee.DepartmentID, 
+    (department, employeeGroup) => new 
+        { 
+            Department = department.Name, 
+            Employees = employeeGroup.Select(e => e.Name).ToList() 
+        }
+);
+```
 
 ### 结果转换
-
 <!--rehype:wrap-class=col-span-2&style=background:#e91e63;-->
 
 ```cs
@@ -1272,8 +1265,6 @@ Student firstStudent = result.First();
 Student firstStudent = result.FirstOrDefault();
 ```
 
-
-
 ### 自定义扩展方法
 
 ```cs
@@ -1293,14 +1284,12 @@ public static class CustomExtensions
 // 使用自定义扩展方法
 var filteredData = students.CustomFilter(s => s.Age > 20);
 ```
-
 <!--rehype:className=wrap-text-->
 
 ### 示例
-
 <!--rehype:wrap-class=col-span-3&style=background:#e91e63;-->
 
-> 假设有一个包含学生信息的列表，每个学生有姓名、年龄和成绩。使用LINQ查询来选择年龄大于20岁的学生，然后按照他们的成绩进行分组，并选择每个分组中年龄最小的学生的姓名。
+假设有一个包含学生信息的列表，每个学生有姓名、年龄和成绩。使用LINQ查询来选择年龄大于20岁的学生，然后按照他们的成绩进行分组，并选择每个分组中年龄最小的学生的姓名。
 
 ```cs
 // 示例数据源
@@ -1314,15 +1303,21 @@ List<Student> students = new List<Student>
     new Student { Name = "Damon", Age = 28, Grade = "B" },
     new Student { Name = "Echo", Age = 18, Grade = "C" }
 };
+```
 
-// 使用LINQ进行查询
+使用 `LINQ` 进行查询
+
+```cs
 var result = students
     .Where(student => student.Age > 20) // WHERE: 选择年龄大于20的学生
     .GroupBy(student => student.Grade)  // GROUP BY: 按成绩分组
     .Select(group => group.OrderBy(student => student.Age).First().Name) // SELECT: 选择每个分组中年龄最小的学生的姓名
     .ToList(); //转换为List<Student>()
+```
 
-//输出结果
+输出结果
+
+```cs
 ["Charlie","Damon","David"]
 ```