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

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code first实现自关联(树结构数据)

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