为什么 List<int> 是空的，即使我向它添加了值？ C＃

Question

我有一个问题，我基本上知道答案。我想知道为什么新创建的List<int> 是空的，为什么即使我用值填充它也是空的？我可以轻松地在类 Vysvedceni(ReportCard) 列表中创建它，然后在 Main 类中创建一个单独的字段，然后将其添加到 Dictionary<Enum,List<int>> ...

类似的东西：

List<Enum,List<int>> array = new ...
array.Add(1);
array.Add(2);
array.Add(5);
dic[Subject].Add(array);

但我想换一种方式：

Student student = new Student("Jan", "Novak",new Vysvedceni());
student.Vysvedceni.Znamky.Add(Vysvedceni.Subjects.math, new List<int>() {1,1,2,3,4,3});

我的目标很简单，打印带有学生及其分数的字典。
我的母语不是英语，我想把代码翻译一下，但我怕你复制代码会弄得一团糟。至少我添加了一个小翻译。 我还添加了我的评论，问题出在哪里或有什么方法。

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

namespace Cviceni1412
{
    class Student
    {
        private string jmeno; //Name
        private string prijmeni; //Surname
        private Vysvedceni vysvedceni;
        //Dictionary<List<Student>, List<Vysvedceni>> vysvedceniTridy = new Dictionary<List<Student>, List<Vysvedceni>>();
    
        List<Student> studenti = new List<Student>();

        public void SetridStudenty()
        {
            var setrid = (from student in studenti select student)
                .GroupBy(student => student.Jmeno.First()).ToList();
            foreach (var item in setrid)
            {
                Console.WriteLine(item);
            }
        }
    
        public override string ToString()
        {
            return "jmeno:"+jmeno + ",prijmeni:" + prijmeni;
        }
    
        public Student(string jmeno, string prijmeni, Vysvedceni vysvedceni)
        {
            this.jmeno = jmeno;
            this.prijmeni = prijmeni;
            this.vysvedceni = vysvedceni;
        }
    
        public string Jmeno { get => jmeno; set => jmeno = value; }
        public string Prijmeni { get => prijmeni; set => prijmeni = value; }
        internal Vysvedceni Vysvedceni { get => vysvedceni; set => vysvedceni = value; }
    }
}

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

namespace Cviceni1412
{
    class Vysvedceni
    {
        private Dictionary<Enum, List<int>> znamky = new Dictionary<Enum, List<int>>();
        private Dictionary<Enum, int> vizo = new Dictionary<Enum, int>();
        private Predmety skolniPredmety;

        public Dictionary<Enum, List<int>> Znamky { get => znamky; set => znamky = value; }
        internal Predmety SkolniPredmety { get => skolniPredmety; set => skolniPredmety = value; }
        public Dictionary<Enum, int> Vizo{ get => vizo; set => vizo= value; }

        public double Prumer(Enum predmet) //Method for calulating Average and final mark for student
        {
            double prumerZnamka=Znamky[predmet].Average();
           
            return prumerZnamka ;
        }

        public void Vypis()//Print List method
        {
            Znamky.Select(i => $"{i.Key}:{i.Value}").ToList().ForEach(Console.WriteLine);
        }

        public Vysvedceni()
        {
        }

        public enum Predmety//Subjects like math,Engl,P.E.,Physic
        {
            matematika,cestina,fyzika,programovani,telocvik,databaze,webovky
        }
    }
}

//Student class

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

namespace Cviceni1412
{
    class Student
    {
        private string jmeno;
        private string prijmeni;
        private Vysvedceni vysvedceni;
        //Dictionary<List<Student>, List<Vysvedceni>> vysvedceniTridy = new Dictionary<List<Student>, List<Vysvedceni>>();

        List<Student> studenti = new List<Student>();

        public void SetridStudenty()//Sort students to the group by their first letter
        {
            var setrid = (from student in studenti select student)
                .GroupBy(student => student.Jmeno.First()).ToList();
            foreach (var item in setrid)
            {
                Console.WriteLine(item);
            }
        }

        public override string ToString()
        {
            return "jmeno:"+jmeno + ",prijmeni:" + prijmeni;
        }

        public Student(string jmeno, string prijmeni, Vysvedceni vysvedceni)
        {
            this.jmeno = jmeno;
            this.prijmeni = prijmeni;
            this.vysvedceni = vysvedceni;
        }

        public string Jmeno { get => jmeno; set => jmeno = value; }
        public string Prijmeni { get => prijmeni; set => prijmeni = value; }
        internal Vysvedceni Vysvedceni { get => vysvedceni; set => vysvedceni = value; }
    }
}

//Main class
using System;
using System.Collections.Generic;
using System.Linq;

namespace Cviceni1412
{
    class Program
    {
        static void Main(string[] args)
        {
            Student student = new Student("Jan","Novák",new Vysvedceni());
            student.Vysvedceni.Znamky.Add(Vysvedceni.Predmety.matematika, new List<int>() {1,1,2,3,4,3 });//There is problem,List is declared and filled,but it prints just only Subject and [System.Generics...]

            Console.WriteLine(student.Vysvedceni.Znamky.Keys.Count);
            student.Vysvedceni.Vypis();  
        }
    }
}

Answer 1

我是如何解决的。 问题不在于 ToString() 方法，而在于 Print() 方法。Linq 只迭代了 Keys。希望我能帮上忙

public void Print(Subjects sub)
{
    foreach (var item in marks//dictionary)
    {
        Console.WriteLine(item.Key);
  
        foreach (var ite in marks[sub])
        {
             Console.WriteLine(ite);
        }
    }
}