C# 程序存储多个学生记录，包括姓名、1-5 年级和平均成绩

Question

我正在尝试创建一个程序，该程序接受用户输入的学生数量，然后考虑到提示 5 个成绩和每个学生的平均成绩。

学生记录示例如下：

学生#...... Grade1..... Grade2..... Grade3..... Grade4..... Grade5.....平均

到目前为止的代码（无论如何可能都不正确）：

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Question_Two
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Input the number of students: ");
            int n = int.Parse(Console.ReadLine()); 
            Student[] students = new Student[6];

            string studentId = "Student 1"; //error here
            students[0].addGrade(double.Parse(studentId)); // or error here

            double value;
            value = double.Parse(Console.ReadLine());
            students[1].addGrade(value);

            value = double.Parse(Console.ReadLine());
            students[2].addGrade(value);

            value = double.Parse(Console.ReadLine());
            students[3].addGrade(value);

            value = double.Parse(Console.ReadLine());
            students[4].addGrade(value);

            value = double.Parse(Console.ReadLine());
            students[5].addGrade(value);

            students[6].getAverage();
        }

        public class Student
        {
            private ArrayList grades;

            public Student()
            {
                grades = new ArrayList();
            }

            public void addGrade(double val)
            {
                grades.Add(val);
            }

            public double getAverage()
            {
                double avg = 0;
                for (int i = 0; i < grades.Count; i++)
                {
                    avg += (double)grades[i];
                }
                avg /= grades.Count;
                return avg;
            }
        }
    }
}

我不确定从这里去哪里，因为在将名称存储到数组时出错。

Answer 1

使用new 创建数组不会创建每个单独的元素（int 等基元除外）。您需要为数组中的每个项目调用new：

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Input the number of students: ");
        int n = int.Parse(Console.ReadLine()); 

        // Create array of size n (instead of 6)
        // Array is created but individual Students are not created yet!
        Student[] students = new Student[n];

        // Use a loop to get all student info
        for (int s = 0; s < n; s++) {
            string studentId = $"Student{s+1}";

            // Important! Need to create a student object
            students[s] = new Student(studentId);

            // Use another loop to get grades
            for (int g = 0; g < 5; g++) {
                double grade = double.Parse(Console.ReadLine());
                students[s].addGrade(grade);
            }

            // Print average
            Console.WriteLine($"{students[s].id} average = {students[s].getAverage()}");
        }
    }

另外，修改Student 类以具有id

    public class Student
    {
        private ArrayList grades;
        public string id;

        // Accepts one parameter : an id
        public Student(string studentId)
        {
            id = studentId;
            grades = new ArrayList();
        }

        public void addGrade(double val)
        {
            grades.Add(val);
        }

        public double getAverage()
        {
            double avg = 0;
            for (int i = 0; i < grades.Count; i++)
            {
                avg += (double)grades[i];
            }
            avg /= grades.Count;
            return avg;
        }
    }
}

Answer 2

您不能像下面的代码那样将字符串“Student 1”解析为双精度：

   string studentId = "Student 1"; //error here
   students[0].addGrade(double.Parse(studentId)); 

我不知道你想要的结果是什么。但请确保学生 id 是一个数值（可以是字符串形式）。你可以使用下面的代码来得到你想要的。

        Console.WriteLine("Input the number of students: ");
        int numberOfStudents = int.Parse(Console.ReadLine());

        Student student = new Student();

        string studentId = "1";
        student.addGrade(double.Parse(studentId));

        double value;
        value = double.Parse(Console.ReadLine());
        student.addGrade(value);

        value = double.Parse(Console.ReadLine());
        student.addGrade(value);

        value = double.Parse(Console.ReadLine());
        student.addGrade(value);

        value = double.Parse(Console.ReadLine());
        student.addGrade(value);

        value = double.Parse(Console.ReadLine());
        student.addGrade(value);

        double avarageNumber = student.getAverage();