使用LINQ返回子对象

// 假设有一个包含学生信息的类
public class Student
{
    public string Name { get; set; }
    public int Age { get; set; }
    public List<string> Courses { get; set; }
}

// 创建学生对象集合
List<Student> students = new List<Student>
{
    new Student { Name = "Alice", Age = 20, Courses = new List<string> { "Math", "English" } },
    new Student { Name = "Bob", Age = 22, Courses = new List<string> { "Physics", "Chemistry" } },
    new Student { Name = "Charlie", Age = 21, Courses = new List<string> { "History", "Geography" } }
};

// 使用LINQ查询表达式返回年龄大于等于21岁的学生的课程列表
var courses = from student in students
              where student.Age >= 21
              select student.Courses;

// 使用LINQ方法语法返回年龄大于等于21岁的学生的课程列表
var courses = students.Where(student => student.Age >= 21).Select(student => student.Courses);