IEnumerable<T>的應用

寫兩個類一個是學生、一個是班級。邏輯上學生是屬於班級這個集合的，按理來說是可以直接使用foreach直接遍歷出班級裡面的學生。但是由於ClassOfStudent未實現 IEnumerable或IEnumerable<T>介面

出現編譯報錯：“ClassOfStudent”不包含“GetEnumerator”的公共例項或擴充套件定義，因此 foreach 語句不能作用於“ClassOfStudent”型別的變數

  public class Test
    {

        static void Main(string[] args)
        {

            Student[] st 
 
= new Student[2];
            ClassOfStudent ClassTwoOfTheThirdYear = new ClassOfStudent();
            ClassTwoOfTheThirdYear.AddStudent(new Student { Name = "xsdfsdf", Age = 12 });
            ClassTwoOfTheThirdYear.AddStudent(new Student { Name = "xsdff", Age = 12 });
//ClassOfStudent未實現 IEnumerable或IEnumerable<T>介面時候編譯器報錯：
 
//“ClassOfStudent”不包含“GetEnumerator”的公共例項或擴充套件定義，因此 foreach 語句不能作用於“ClassOfStudent”型別的變數

            foreach (var stu in ClassTwoOfTheThirdYear)
            {
                Console.WriteLine(stu.Name);

            }

        }
    }
    

    public class Student : IComparable<Student>
    {
        
 
private string name;
        private int age;
        private int dage;

        public string Name
        {
            get => name;
            set
            {
                if (string.IsNullOrEmpty(value)) throw new ArgumentException("不能使用空白名稱", "Name");
                name = value;
            }
        }


        public int Age { get => age; set => age = value; }
        public int Dage { get => dage; set => dage = value; }

        public string this[string name]
        {

            get => name;
            set
            {

                name = value;
            }
        }
        //過載比較方法
        public int CompareTo(Student st)
        {


            return this.name.CompareTo(st.name);

        }
        //過載 ToString（）方法
        public override string ToString()
        {
            return string.Format($"姓名：{this.name} 年齡：{this.age}");
        }
        //過載操作符 +
        public static Student operator +(Student st, Student st1)
        {

            return new Student { Name = st.name + st1.name, Age = st.age + st1.age };
        }
        public static implicit operator Student(int st)

        {

            return new Student { Name = "", Age = st };
        }
        public static explicit operator int(Student st)
        {

            return st.Age;

        }
    }
    public class ClassOfStudent
    {

        private string className;
        private int studentNumber;
        private List<Student> students;

        public string ClassName { get => className; set => className = value; }

        public int StudentNumber { get => studentNumber; set => studentNumber = value; }

        public void AddStudent(Student st)
        {

            students.Add(st);

        }



    }