code first实现自关联(树结构数据)

实现自关联数据时，有两点须注意：

1.外键字段必须设置为可为空的值类型(如int?;Guid?等)

2.设置映射时不能级联删除,要设置WillCascadeOnDelete(false)

二话不说了，直接来代码：

一.部门实体:

/// <summary>

        /// 部门名

        /// </summary>

        public string Name { get; set; }



        /// <summary>

        /// 部门编号

        /// </summary>

        public string Code { get; set; }



        /// <summary>

        /// 父级部门ID

        /// </summary>

        public Guid? ParentId { get; set; }



        /// <summary>

        /// 部门顺序号(同级)

        /// </summary>

        public int Order { get; set; }



        /// <summary>

        /// 父级部门

        /// </summary>

        public virtual Department ParentDepartment { get; set; }



        /// <summary>

        /// 当前部门下的员工(不包含子部门的)

        /// </summary>

        public virtual ICollection<Employee> Employees { get; set; }



        /// <summary>

        /// 当前部门的子部门(不包含子部门的下级部门)

        /// </summary>

        public virtual ICollection<Department> ChildrenDepartments { get; set; }

二.实体的映射配置

public class DepartmentEntityConfig:EntityTypeConfiguration<Department>

    {

        #region 成员变量



        #endregion



        #region 构造函数



        public DepartmentEntityConfig()

        {

            this.HasKey(d => d.Id);



            this.Property(d => d.Name)

                .IsRequired()

                .HasMaxLength(50);



            this.Property(d => d.Code)

                .IsRequired()

                .HasMaxLength(10);



            this.Property(d => d.Order)

                .IsRequired();



            this.Property(d => d.ParentId)

                .IsOptional();



            this.HasOptional(d => d.ParentDepartment)

                .WithMany(c => c.ChildrenDepartments)

                .HasForeignKey(d => d.ParentId)

                .WillCascadeOnDelete(false);

               



            this.ToTable("Department");

        }



        #endregion



        #region 属性



        #endregion



        #region 方法



        #endregion

    }

 一定注意加红色的部分，搞了我好久