C#_IEnumerable和IEnumerable

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

namespace CShapeTest
{
    // 實現非泛型IEnumerable可枚舉接口
    class Teacher:IEnumerable
    {
        private List<Student> stuList;

        public Teacher()
        {
            stuList = new List<Student>();
        }

        public void add(Student stu)
        {
            this.stuList.Add(stu);
        }

        public IEnumerator GetEnumerator()
        {
            return this.stuList.GetEnumerator();
        }
    }

    class Student
    {
        private int age;
        private string name;

        public Student(int age, string name)
        {
            this.age = age;
            this.name = name;
        }

        public override string ToString()
        {
            return string.Format("age:{0}, name:{1}", this.age, this.name);
        }
    }

    class Start
    {
        static void Main(string[] args)
        {
            Teacher tea = new Teacher();
            tea.add(new Student(20, "cxm"));
            tea.add(new Student(23, "zqr"));
            tea.add(new Student(25, "chenglong"));
            tea.add(new Student(27, "xiaoming"));
            tea.add(new Student(30, "lisi"));

            foreach (var item in tea)
            {
                Console.WriteLine(item);
            }

            Console.ReadLine();
        }
    }
}

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

namespace CShapeTest
{
    // 實現泛型IEnumerable<T>可枚舉接口
    class Teacher:IEnumerable<Student>
    {
        private List<Student> stuList;

        public Teacher()
        {
            stuList = new List<Student>();
        }

        public void add(Student stu)
        {
            this.stuList.Add(stu);
        }

        //可枚舉的類可以返回枚舉  
        public IEnumerator<Student> GetEnumerator()
        {
            foreach (Student s in stuList)
            {
                yield return s;
            }
        } 

        //顯式實現接口  
        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        } 
    }

    class Student
    {
        private int age;
        private string name;

        public Student(int age, string name)
        {
            this.age = age;
            this.name = name;
        }

        public override string ToString()
        {
            return string.Format("age:{0}, name:{1}", this.age, this.name);
        }
    }

    class Start
    {
        static void Main(string[] args)
        {
            Teacher tea = new Teacher();
            tea.add(new Student(20, "cxm"));
            tea.add(new Student(23, "zqr"));
            tea.add(new Student(25, "chenglong"));
            tea.add(new Student(27, "xiaoming"));
            tea.add(new Student(30, "lisi"));

            foreach (var item in tea)
            {
                Console.WriteLine(item);
            }

            Console.ReadLine();
        }
    }
}