public class Student

{

    public int ID { get; set; }

    public string Name { get; set; }

    //[XmlIgnore]

    public Grade Grade { get; set; }

}

public class Grade

{

    public int GradeID { get; set; }

    public string GradeName { get; set; }

    public List<Student> Students { get; set; }

}

//创建班级

Grade gradeOne = new Grade() { GradeID = , GradeName = "班级1" };

gradeOne.Students = new List<Student>();

//添加班级下的学生

Student stu = new Student();

stu.ID = ;

stu.Name = "张三";

//设置学生所属的班级

/*

    * 1.如果指定学生的班级 就会抛出异常：序列化类型 Test.Grade 的对象时检测到循环引用。

    * 2.解决方法1：在创建的时候不指定子类对应的父类

    * 3.解决方法2：在子类的父类对象属性，添加[XmlIgnore]

    */

stu.Grade = gradeOne;

gradeOne.Students.Add(stu);

XmlSerializer xmls = new XmlSerializer(gradeOne.GetType());

string content;

using (MemoryStream ms = new MemoryStream())

{

    xmls.Serialize(ms, gradeOne);

    ms.Position = ;

    using (StreamReader reader = new StreamReader(ms))

    {

        content = reader.ReadToEnd();

    }

}

Console.WriteLine(content);