如何使用linQ进行分组连接

// 假设有两个实体类：Student和Course
class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int CourseId { get; set; }
}

class Course
{
    public int Id { get; set; }
    public string Name { get; set; }
}

// 假设有两个集合：students和courses
List<Student> students = new List<Student>
{
    new Student { Id = 1, Name = "Alice", CourseId = 1 },
    new Student { Id = 2, Name = "Bob", CourseId = 1 },
    new Student { Id = 3, Name = "Charlie", CourseId = 2 },
    new Student { Id = 4, Name = "David", CourseId = 2 },
};

List<Course> courses = new List<Course>
{
    new Course { Id = 1, Name = "Math" },
    new Course { Id = 2, Name = "English" },
};

// 使用LINQ进行分组连接
var result = from student in students
             join course in courses on student.CourseId equals course.Id
             group student by course.Name into g
             select new
             {
                 CourseName = g.Key,
                 Students = g.ToList()
             };

// 输出结果
foreach (var item in result)
{
    Console.WriteLine("Course: " + item.CourseName);
    foreach (var student in item.Students)
    {
        Console.WriteLine("  Student: " + student.Name);
    }
}