C#迭代器foreach

自己建立的类中，可以通过迭代器列出所有的成员   

需用到   IEnumerable

建立   Students  类，通过迭代列出所有的student的id和name 

    class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
    class Students :IEnumerable
    {
        public List<Student> students = new List<Student>();
        public void Add(int id,string name) => students.Add(new Student { Id=id,Name=name});
       
        public IEnumerator GetEnumerator()
        {
            foreach (var s in students)
            {
                yield return s;
            }
        }
    }

新建一个按钮和文本框，写入代码

        private void button1_Click(object sender, EventArgs e)
        {
            Students st = new Students();
            st.Add(0, "Tony");
            st.Add(1, "Micheal");
            st.Add(2, "Amy");
            foreach (var s in st)
            {
                Student st1 = (Student)s;

                  textBox1.AppendText(st1.Id.ToString() +":"+ st1.Name+"\r\n");

            }
        }