ASP.NET 添加遷移'復合主鍵錯誤' 如何使用 fluent API

Question

您好，我正在創建 Web 應用程序，並且已經安裝了Microsoft.entityFrameworkCore和Microsoft.entityFrameworkCore.Tools 。

在包管理器控制台中執行添加遷移的過程中，我收到一個錯誤

" System.InvalidOperationException: 實體類型 'Attends' 具有使用數據注釋定義的復合主鍵。要設置復合主鍵，請使用 fluent API "

這是我在實體文件夾中的代碼。

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; }
    }
}

如何調整它以正確設置復合鍵？

Answer 1

在EF 核心上..

復合鍵只能使用 Fluent API 進行配置 - 約定永遠不會設置復合鍵，並且您不能使用數據注釋來配置一個。

這是Fluent API版本：

注意：這只是一個例子。 請根據您的用例進行調整。

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

您可以在此處閱讀更多相關信息： 復合鍵