EF实体类,设置导航属性,导致序列化时出现"循环引用"错误,及序列化时间格式解决方案

三个实体类,学生类(Student),班级类(StudentClass),年级类(Grade)

学生类与班级类为多对一的关系,班级表的主键为学生表的外键,年级表的主键为学生表的外键

public class Student
    {
        [Column("StudentId")]
        public int Id { get; set; }

        [Required]
        [StringLength(200)]
        public string _Name { get; set; }
        public int _Sex { get; set; }
        public DateTime _Birthday { get; set; }

        public DateTime _AddTime { get; set; }

        public virtual Department Department { get; set; }

        public virtual Grade Grades { get; set; }

        public virtual StudentClass studentclass { get; set; }

      
    }


 public class StudentClass
    {
        [Key]
        [Column("ClassId")]
        public int Id { get; set; }

        [Required]
        [StringLength(30)]
        public string ClassName { get; set; }

        public virtual ICollection<Student> student { get; set; }

        public virtual Department department { get; set; }

        public virtual Grade grade { get; set; }
    }

public class Grade
    {
        [Key]
        public int GradeId { get; set; }

        [StringLength(30)]
        [Required]
        public string GradeName { get; set; }

        [StringLength(200)]
        public string GradeExplain { get; set; }

        public virtual ICollection<Student> student { get; set; }

        public virtual List<StudentClass> studentclass { get; set; }

        public virtual Department department { get; set; }
    }

  查询学生实体类,获取学生实体列表:

      var Studentlist = db.Students.OrderByDescending(s => s.Id).Skip(IntDataPageSize * (IntDataPageIndex - 1)).Take(IntDataPageSize).ToList();

      使用Newtonsoft.Json反序列化,给前端返回json字符串

      string json = JsonConvert.SerializeObject(Studentlist );

     报错,循环引用

    解决方案:

  

 JsonSerializerSettings jsSettings = new JsonSerializerSettings();
                jsSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
                string Datastr = JsonConvert.SerializeObject(classlist, jsSettings);

  

这样返回json成功,但是列表里面有时间,时间格式异常,没有显示正确的时间格式,

经过摸索,找到解决方案,直接上代码:

JsonSerializerSettings jsSettings = new JsonSerializerSettings();
            jsSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
jsSettings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
            string Datastr = JsonConvert.SerializeObject(Studentlist,Formatting.Indented,jsSettings);

  问题解决!

      有认说,使用这种方案,不能反序列化,目前没实践过,但是在查找资料的时候,有篇文章,介绍了这种情况的解决方案,直接上地址:

   https://blog.csdn.net/xxdddail/article/details/82252765,有空可以实践一下

posted @ 2019-01-14 23:22  一夜听春雨  阅读(924)  评论(1编辑  收藏  举报