如何使用linq进行计数和分组

// 假设有一个包含学生信息的对象集合
List<Student> students = new List<Student>
{
    new Student { Name = "张三", Age = 20, Grade = "一年级" },
    new Student { Name = "李四", Age = 21, Grade = "二年级" },
    new Student { Name = "王五", Age = 20, Grade = "一年级" },
    new Student { Name = "赵六", Age = 22, Grade = "三年级" },
    new Student { Name = "钱七", Age = 21, Grade = "二年级" }
};

// 使用LINQ进行计数操作
int count = students.Count();
Console.WriteLine("学生总数：" + count);

// 使用LINQ进行分组操作
var groups = students.GroupBy(s => s.Grade);
foreach (var group in groups)
{
    Console.WriteLine("年级：" + group.Key);
    Console.WriteLine("人数：" + group.Count());
    foreach (var student in group)
    {
        Console.WriteLine("姓名：" + student.Name);
    }
    Console.WriteLine();
}

public class Student
{
    public string Name { get; set; }
    public int Age { get; set; }
    public string Grade { get; set; }
}