使用构造函数C＃将项目添加到列表

Question

I am learning C# and was trying different ways to add to list. I tried two different method below . First One does not work , second one does work .

What is wrong with first method?

 class Program
    {
        static void Main(string[] args)
        {
            Employee emps = new Employee();
            emps.PromoteEmp(emps.emp);
        }
    }

    class Employee
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int Salary { get; set; }
        public int Experience { get; set; }
        public List<Employee> emp;

        public Employee()
        {
            emp = new List<Employee>();
            emp.Add(new Employee() { ID = 1, Name = "A", Experience = 6, Salary = 30000 });
            emp.Add(new Employee() { ID = 2, Name = "B", Experience = 4, Salary = 10000 });
            emp.Add(new Employee() { ID = 1, Name = "C", Experience = 5, Salary = 15000 });
            emp.Add(new Employee() { ID = 1, Name = "D", Experience = 8, Salary = 60000 });
        }

        public void PromoteEmp(List<Employee> empList)
        {
            foreach (Employee item in empList)
            {
                if (item.Experience > 5)
                {
                    Console.WriteLine(item.Name + " promoted ");
                }
            }
        }
    }

Second Method

 class Program
    {
        static void Main(string[] args)
        {
            Employee emps = new Employee();
            emps.AddToList();
            emps.PromoteEmp(emps.emp);
        }
    }

    class Employee
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int Salary { get; set; }
        public int Experience { get; set; }
        public List<Employee> emp;


        public void AddToList()
        {
          emp = new List<Employee>();
          emp.Add(new Employee() { ID = 1, Name = "A", Experience = 6, Salary = 30000 });
          emp.Add(new Employee() { ID = 2, Name = "B", Experience = 4, Salary = 10000 });
         emp.Add(new Employee() { ID = 1, Name = "C", Experience = 5, Salary = 15000 });
         emp.Add(new Employee() { ID = 1, Name = "D", Experience = 8, Salary = 60000 });
        }

        public void PromoteEmp(List<Employee> empList)
        {
            foreach (Employee item in empList)
            {
                if (item.Experience > 5)
                {
                    Console.WriteLine(item.Name + " promoted ");
                }
            }
        }
    }

Thank You :)

Answer 1

It's easy, in the first case you construct your Employee which constructs more Employee s and so on and so forth.

In fact if you bothered to paste the exception you got, it would be readily obvious: StackOverflowException .

Answer 2

您的第一个代码会导致无限循环，因为要在Constructor中添加相同的Employee类。

Answer 3

Actually, program goes to infinite loop in constructor and never complete.

In Main():

from this line : Employee emps = new Employee();

program goes to constructor to initialize object.

Now in constructor:

emp.Add(new Employee() { ID = 1, Name = "A", Experience = 6, Salary = 30000 });

At this line, you are adding new Employee object to list. Here object initialization again, and thus program goes to infinite loop in constructor.

Your program will never reach at final line.