用c#编写一个程序读取附件（附件文件是一个文本文件，可以用记事本打开查看）完成如下要求： 1） 计算所有人的总分，并设为新的一列“总分”，并存储到磁盘 2） 输出1、2班 以及合班 三份总分的降序排名 3） 求解1、2班各自的各科平均分

好的，以下是一个基于您的要求的 C# 程序实现，假设附件文件名为 "scores.txt"：

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

class Program
{
    static void Main(string[] args)
    {
        // 读取附件文件
        var lines = File.ReadAllLines("scores.txt");
        // 解析每行数据
        var students = lines.Select(line =>
        {
            var fields = line.Split(',');
            var student = new Student
            {
                Class = int.Parse(fields[0]),
                Name = fields[1],
                MathScore = int.Parse(fields[2]),
                EnglishScore = int.Parse(fields[3]),
                ChineseScore = int.Parse(fields[4])
            };
            return student;
        }).ToList();

        // 计算每个学生的总分
        foreach (var student in students)
        {
            student.TotalScore = student.MathScore + student.EnglishScore + student.ChineseScore;
        }

        // 将总分保存到磁盘
        var outputLines = students.Select(student =>
            $"{student.Class},{student.Name},{student.MathScore},{student.EnglishScore},{student.ChineseScore},{student.TotalScore}");
        File.WriteAllLines("scores_with_total.txt", outputLines);

        // 计算总分排名
        var totalScores = students.Select(student => student.TotalScore);
        var overallRanking = totalScores.OrderByDescending(score => score).ToList();
        var class1Ranking = totalScores.Where(score => students.Where(s => s.Class == 1).Select(s => s.TotalScore).Contains(score)).OrderByDescending(score => score).ToList();
        var class2Ranking = totalScores.Where(score => students.Where(s => s.Class == 2).Select(s => s.TotalScore).Contains(score)).OrderByDescending(score => score).ToList();

        // 输出总分排名
        Console.WriteLine("Overall ranking:");
        for (int i = 0; i < overallRanking.Count; i++)
        {
            Console.WriteLine($"{i + 1}. {overallRanking[i]}");
        }

        Console.WriteLine("Class 1 ranking:");
        for (int i = 0; i < class1Ranking.Count; i++)
        {
            Console.WriteLine($"{i + 1}. {class1Ranking[i]}");
        }

        Console.WriteLine("Class 2 ranking:");
        for (int i = 0; i < class2Ranking.Count; i++)
        {
            Console.WriteLine($"{i + 1}. {class2Ranking[i]}");
        }

        // 计算平均分
        var class1MathAverage = students.Where(s => s.Class == 1).Average(s => s.MathScore);
        var class1EnglishAverage = students.Where(s => s.Class == 1).Average(s => s.EnglishScore);
        var class1ChineseAverage = students.Where(s => s.Class == 1).Average(s => s.ChineseScore);
        var class2MathAverage = students.Where(s => s.Class == 2).Average(s => s.MathScore);
        var class2EnglishAverage = students.Where(s => s.Class == 2).Average(s => s.EnglishScore);
        var class2ChineseAverage = students.Where(s => s.Class == 2).Average(s => s.ChineseScore);

        Console.WriteLine($"Class 1 math average: {class1MathAverage}");
        Console.WriteLine($"Class 1 English average: {class1EnglishAverage}");
        Console.WriteLine($"Class 1 Chinese average: {class1ChineseAverage}");
        Console.WriteLine($"Class 2 math average: {class2MathAverage}");
        Console.WriteLine($"Class 2 English average: {class2EnglishAverage}");
        Console.WriteLine($"Class 2 Chinese average: {class2ChineseAverage}");
    }
}

class Student
{
    public int Class { get; set; }
    public string Name { get; set; }
    public int MathScore { get; set; }
    public int EnglishScore { get; set; }
    public int ChineseScore { get; set; }
    public int TotalScore { get; set; }
}

这个程序首先读取附件文件，解析每行数据并创建一个 `Student` 对象的列表。然后，它计算每个学生的总分，并将结果保存到一个新的文件中。接下来，它计算总分排名，并输出1、2班和合班的排名。最后，它计算每个班级的各科平均分，并输出结果。