ASP.NET添加迁移'复合主键错误'如何使用流畅的API

Question

您好我正在创建Web应用程序,并且已经安装了Microsoft.entityFrameworkCore和Microsoft.entityFrameworkCore.Tools.

在包管理器控制台中执行添加迁移的过程中,我收到错误

" System.InvalidOperationException:实体类型'Attends'具有使用数据注释定义的复合主键.要设置复合主键,请使用流畅的API "

这是我在实体文件夹中的代码.

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Threading.Tasks;

namespace _3241_farmDb.Entities
{

    public class Farm
    {
        [Required, MaxLength(30)]
        [Key]
        public string FarmName { get; set; }
        [Required, MaxLength(15)]
        public string FarmCity { get; set; }
        [Required, MaxLength(9)]
        public string FarmerSSN { get; set; }
    }
    public class Farmer
    {
        [Required, MaxLength(9)]
        [Key]
        public int SS { get; set; }
        [Required, MaxLength(9)]
        public string Fname { get; set; }
        [Required, MaxLength(15)]
        public string Lname { get; set; }
        [Required, MaxLength(15)]
        public string CityName { get; set; }
        [Required, MaxLength(15)]
        public string Address { get; set; }
        [Required, MaxLength(30)]
        public string BoardPositionName { get; set; }
    }
    public class Child
    {
        [Required, MaxLength(9)]
        [Key]
        public int FarmerSS { get; set; }
        [Required, MaxLength(15)]
        [Key]
        public string Fname { get; set; }
        [Required, MaxLength(15)]
        [Key]
        public string Lname { get; set; }
        [Required]
        public int Age { get; set; }
    }
    public class Attends
    {

        [Key, Column(Order = 1)]
        public int FarmerSS { get; set; }
        [Key, Column(Order = 2)]
        public int HotelID { get; set; }
        [Required, MaxLength(15)]
        public string BoardPosition { get; set; }
    }

    public class Livestock
    {
        [Required, MaxLength(15)]
        public int LivestockID { get; set; }
        [Required, MaxLength(15)]
        public string LivestockType { get; set; }
    }
    public class Farm_Houses
    {
        [Required, MaxLength(15)]
        [Key]
        public int LivestockID { get; set; }
        [Required, MaxLength(15)]
        public string FarmName { get; set; }
    }
    public class Crops
    {
        [Required, MaxLength(15)]
        [Key]
        public int CropID { get; set; }
        [Required, MaxLength(15)]
        public string CropName { get; set; }
    }
}

如何调整它以正确设置复合键？

Answer 1

在EF核心..

复合键只能使用Fluent API进行配置 - 约定永远不会设置复合键,也不能使用Data Annotations来配置复合键.

这是Fluent API版本:

注意:这只是一个例子.请根据您的使用情况进行调整.

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Attends>()
        .HasKey(c => new { c.FarmerSS, c. HotelID });
}

你可以在这里阅读更多相关信息:复合键