如何使用LINQ按姓氏首字母对学生进行分组？

你的代码存在两个核心问题，导致没有输出且未完成「按姓氏首字母分组」的需求：

• 仅提取了学生姓氏的首字母，未实现分组逻辑
• 完全没有添加输出代码，终端自然不会显示内容

修正后的代码 #

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        // Student collection
        List<Student> studentList = new List<Student>() { 
            new Student {First="Bob", Last="Jones", ID=111, Age=15, Scores= 5},
            new Student {First="Bob", Last="Jones", ID=111, Age=15, Scores= 10},
            new Student {First="Claire", Last="Simpson", ID=112, Age=17, Scores= 5},
            new Student {First="John", Last="Feetham", ID=113, Age=21, Scores= 10},
            new Student {First="Jonathan", Last="Potts", ID=114, Age=10, Scores= 10},
            new Student {First="Pepe", Last="Garcia", ID=115, Age=20, Scores= 5},
            new Student {First="Samantha", Last="Fakhouri", ID=116, Age=17, Scores= 5},
            new Student {First="Roger", Last="Song", ID=117, Age=19, Scores= 5},
            new Student {First="Hugo", Last="Garcia", ID=118, Age=15, Scores= 10},
            new Student {First="Richard", Last="Ammerman", ID=119, Age=14, Scores= 10},
            new Student {First="Kevin", Last="Adamson", ID=120, Age=11, Scores= 10},
            new Student {First="Jeet", Last="Singh", ID=121, Age=12, Scores= 10}
        };

        // 按姓氏首字母分组
        var groupedStudents = studentList.GroupBy(s => s.Last.First());

        // 遍历分组并输出结果
        foreach (var group in groupedStudents)
        {
            Console.WriteLine($"姓氏首字母: {group.Key}");
            foreach (var student in group)
            {
                Console.WriteLine($"  学生: {student.First} {student.Last}, ID: {student.ID}, 年龄: {student.Age}");
            }
            Console.WriteLine(); // 分隔不同分组
        }
    }
}

public class Student{
    public string First { get; set; }
    public string Last { get; set; }
    public int Age { get; set; }
    public int ID { get; set; }
    public int Scores { get; set;}
}

关键修改说明 #

• 用GroupBy(s => s.Last.First())替代原代码的Select，实现按姓氏首字母分组：得到的groupedStudents是分组集合，每个分组的Key为姓氏首字母，分组内包含对应首字母的所有学生。
• 添加两层foreach循环遍历分组结果，并用Console.WriteLine输出每个分组的详细信息，让终端能显示分组内容。

内容的提问来源于stack exchange，提问作者Cutty