在C#中实现自定义类支持“foreach”关键字

    本文介绍在C#中，如何使自定义类支持foreach循环。具体步骤如下：

1、类本身实现要实现IEnumerable接口（或IEnumberable<T>泛型接口）
2、在类的内部定义一个私有的迭代器类（迭代器类当然也可以不是内嵌的私有类），迭代器类需要实现IEnumerator接口（或IEnumberator<T>泛型接口）
用图例来描述上述的工作：
 

 

    下面我们就来自定义一个类StudentCollection，实现该类对foreach的支持。

实例程序类图

StudentCollection类	Student类

 

实例代码

Student类的代码实现：
 class Student
{
 private string name; 
public string Name
{
get { return name; }
set { name = value; }
} 
private int age;
public int Age
{
get { return age; }
set { age = value; }
}
 private string sex;
public string Sex
{
get { return sex; }
set { sex = value; }
}
public Student() { }
public Student(string name,int age,string sex)
 {
 this.name = name;
this.age = age;
this.sex = sex;
}
}

StudentCollection类的代码实现：class StudentCollection : IEnumerable
 {
private string className;
public string ClassName
{
get { return className; }
set { className = value; }
 }
public List<Student> Members = new List<Student>();
#region IEnumerable 成员
public IEnumerator GetEnumerator()
{
return new StudentCollectionEnumerator(this);
}
 #endregion
 private class StudentCollectionEnumerator : IEnumerator
{
private int position = -1;
private StudentCollection collection;
public StudentCollectionEnumerator(StudentCollection collection)
 {
 this.collection = collection;
}
#region IEnumerator 成员
public object Current
{
get { return this.collection.Members[this.position]; }
}
 public bool MoveNext()
{
if (this.position < this.collection.Members.Count - 1)
 {
 this.position++;
return true;
}
else
 {
return false;
}
}
public void Reset()
{
this.position = -1;
 }
 #endregion
 }
 }

Program类的代码实现：

class Program
{
static void Main(string[] args)
{
 StudentCollection students = new StudentCollection();
 students.Members.Add(new Student("张三",10,"男"));
students.Members.Add(new Student("李四",11,"男"));
students.Members.Add(new Student("王五",12,"男"));
students.Members.Add(new Student("小花",10,"女"));
students.Members.Add(new Student("小丽",11,"女"));
foreach(Student student in students)
 {
Console.WriteLine("学生 {0} 的信息：",student.Name);
Console.WriteLine("\t年龄：{0}",student.Age);
 Console.WriteLine("\t性别：{0}\r\n",student.Sex);
 }
Console.ReadLine();
}
}

样例代码运行结果如下：