如何在c#中调用一个方法来显示2个列表?

Question

我有两个列表，studentList(已经制作，我没有问题)和studentList2(从csv文件读取的数据列表)

有效的代码部分是studentList1能够显示类学生和5个对象的部分。然而，对于studentList 2，我能够从csv文件中读取，但无法将2名学生添加到列表中并与studentList 1一起显示。

我试图将相同的概念从第一个列表(这是手动制作的)应用到第二个列表(从csv文件读取)。但我可以看到它显然不工作，我不确定如何解决它。

这是我目前得到的:

using school;
using System.Reflection.PortableExecutable;
DateTime dob1 = new DateTime(2000, 10, 13);
Student s1 = new Student(1, "John Tan", "88552211", dob1);
DateTime dob2 = new DateTime(2001, 11, 01);
Student s2 = new Student(2, "Peter Lim", "85678141", dob2);

DateTime dob3 = new DateTime(2000, 01, 03);
Student s3 = new Student(3, "David Chan", "88555461", dob3);
DateTime dob4 = new DateTime(2000, 05, 07);
Student s4 = new Student(4, "Muhammed Faizal", "98762211", dob4);
DateTime dob5 = new DateTime(2000, 08, 09);
Student s5 = new Student(5, "Esther Eng", "83352245", dob5);
List<Student> studentList = new List<Student>();
studentList.Add(s1); 
studentList.Add(s2);
studentList.Add(s3);
studentList.Add(s4);
studentList.Add(s5);
//call the method to display the student list
DisplayOutput(studentList);
studentList.Add(GetStudent());
DisplayOutput(studentList);
DisplayOutput(studentList2);
//method that displays all the students
static void DisplayOutput(List<Student> sList)
{
    Console.WriteLine("");
    //header id name tel dob
    Console.WriteLine("{0,-5} {1,-17} {2,-10} {3,-20}",
        "ID", "Name", "Tel", "Date of Birth");
    //for loop to print the rest of the info
    foreach (Student s in sList)
    {
        Console.WriteLine("{0,-5} {1,-17} {2,-10} {3,-20}",
           s.ID, s.Name, s.Tel, s.DateOfBirth.ToString("dd/MM/yyyy"));
    }
}
static Student GetStudent()
{
    // prompt user for info
    Console.Write("Enter id: ");
    int id = Convert.ToInt32(Console.ReadLine());
    Console.Write("Enter name: ");
    string? name = Console.ReadLine();
    Console.Write("Enter tel: ");
    string? tel = Console.ReadLine();
    Console.Write("Enter Date of Birth: ");
    DateTime dateOfBirth = Convert.ToDateTime(Console.ReadLine());
    Console.WriteLine("");
    return new Student(id, name, tel, dateOfBirth);
}
//list from the csv
List<Student> studentList2 = new List<Student>();
studentList2.Add(s6);
studentList2.Add(s7);

string[] csvLines = File.ReadAllLines("Students.csv");
string[] heading = csvLines[0].Split(',');
// Read and display lines from the file until the end of
// the file is reached.
for (int i = 1; i < csvLines.Length; i++)
{
    string[] data = csvLines[i].Split(',');
    //Console.WriteLine("{0,-5} {1,-17} {2,-10} {3,-20}",
    //       data[0], data[1], data[2], data[3]);
    Student s6 = new Student(data[0], data[1], data[2], data[3]);
    Student s7 = new Student(data[0], data[1], data[2], data[3]);
}

这是我的类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace school
{
    class Student
    {
        private int id;
        public int ID
        {
            get { return id; }
            set { id = value; }
        }
        private string? name;
        public string? Name
        {
            get { return name; }
            set { name = value; }
        }
        private string? tel;
        public string? Tel
        {
            get { return tel; }
            set { tel = value; }
        }
        private DateTime dateOfBirth;
        public DateTime DateOfBirth
        {
            get { return dateOfBirth; }
            set { dateOfBirth = value; }
        }
        // constructor
        public Student(int d, string? n, string? t, DateTime dob)
        {
            ID = d;
            Name = n;
            Tel = t;
            DateOfBirth = dob;
        }
        // methods
        public string StudentFullName()
        {
            return ID + " " + Name + " " + Tel + " " + DateOfBirth;
        }
    }
}

下面是CSV文件的内容:

ID,Name,Phone,Date of Birth
10,Alan Tan,98552211,13/5/2001
20,Bobby Lim,95678141,8/11/2001

Answer 1

我从你上次的评论中了解到，你需要这样做。

//studentList2.Add(s6); //comment these lines
//studentList2.Add(s7);

string[] csvLines = File.ReadAllLines("Students.csv");
string[] heading = csvLines[0].Split(',');
// Read and display lines from the file until the end of
// the file is reached.
for (int i = 1; i < csvLines.Length; i++)
{
    string[] data = csvLines[i].Split(',');
    //Console.WriteLine("{0,-5} {1,-17} {2,-10} {3,-20}",
    //       data[0], data[1], data[2], data[3]);
    //Student s6 = new Student(data[0], data[1], data[2], data[3]); //also comment these lines
    //Student s7 = new Student(data[0], data[1], data[2], data[3]);
    studentList2.Add(new Student(data[0], data[1], data[2], data[3]));
}

Answer 2

您的代码中似乎有两个问题。

1. studentList2正在初始化学生对象s6和s7之前添加它们。(这应该在编译时错误时出现)。您需要在将其添加到列表之前对其进行初始化。

2. 在创建s6和s7时，您正在读取的数据需要分别转换为int和datetime (data[0]和data[3])。参考上面粘贴的代码。

   List<Student> studentList2 = new List<Student>();
       string[] csvLines = File.ReadAllLines("Students.csv");
       string[] heading = csvLines[0].Split(',');
       // Read and display lines from the file until the end of
       // the file is reached.
       for (int i = 1; i < csvLines.Length; i++)
       {
           string[] data = csvLines[i].Split(',');
           //Console.WriteLine("{0,-5} {1,-17} {2,-10} {3,-20}",
           //       data[0], data[1], data[2], data[3]);
           Student s6 = new Student(Convert.ToInt32(data[0]), data[1], data[2], Convert.ToDateTime(data[3]));
           Student s7 = new Student(Convert.ToInt32(data[0]), data[1], data[2], Convert.ToDateTime(data[3]));
           studentList2.Add(s6);
           studentList2.Add(s7);
       }
       DisplayOutput(studentList2);