流利的Api实体框架核心 [英] Fluent Api Entity Framework core

问题描述

用户可以拥有1个或0个帐户

A user can have 1 or 0 account

public class User
    {
        public int UserId { get; set; }
        public string Name { get; set; }
        public string Email { get; set; }
        public Account Account { get; set; }
    }

    public class Account
    {
        public int AccountId { get; set; }         
        public DateTime CreatedDateTime { get; set; }
        public User User { get; set; }

    }

这是使用Entity Framework 6的流畅api代码。 / p>

This is the fluent api code using Entity Framework 6

public class ClassDbContext: DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

        modelBuilder.Entity<User>()
                  .HasOptional(s => s.Account) 
                  .WithRequired(ad => ad.User);
    }
    public DbSet<User> Users { get; set; }
    public DbSet<Account> Accounts { get; set; }
}

这是结果 ResultImage

使用实体框架核心等效的流畅api代码是什么？

what is the equivalent fluent api code using Entity Framework Core?

推荐答案

@Tseng很近，但还不够。借助建议的配置，您将获得以下消息的异常：

@Tseng is close, but not enough. With the proposed configuration you'll get exception with message:

无法一对一确定子方/从属方在 Account.User和 User.Account之间检测到的关系。要标识关系的子级/从属端，请配置外键属性。请参阅 http://go.microsoft.com/fwlink/?LinkId=724062 更多详细信息。

在文档来自链接。

首先，您需要使用 HasOne 和 WithOne 。

First, you need to use HasOne and WithOne.

第二，您必须使用 HasForeignKey 指定两个实体中的哪个是 dependent （当在其中一个实体中没有定义单独的FK属性时，不会自动检测到它）。

Second, you must use HasForeignKey to specify which one of the two entities is the dependent (it cannot be detected automatically when there is no separate FK property defined in one of the entities).

第三，没有更多所需的依存关系。 IsRequired 方法可用于指定当从属实体使用单独的FK（而不是如您所愿的PK，即所谓的 Shared Primary Key Association ，因为PK显然不能为空）。

Third, there is no more required dependent. The IsRequired method can be used to specify if the FK is required or not when the dependent entity uses separate FK (rather than PK as in your case, i.e. with the so called Shared Primary Key Association because PK apparently cannot be null).

话虽如此，发布模型的正确F核心流利配置为

With that being said, the correct F Core fluent configuration of the posted model is as follows:

modelBuilder.Entity<User>()
    .HasOne(e => e.Account)
    .WithOne(e => e.User)
    .HasForeignKey<Account>(e => e.AccountId);

，结果是：

migrationBuilder.CreateTable(
    name: "User",
    columns: table => new
    {
        UserId = table.Column<int>(nullable: false)
            .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
        Email = table.Column<string>(nullable: true),
        Name = table.Column<string>(nullable: true)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_User", x => x.UserId);
    });

migrationBuilder.CreateTable(
    name: "Account",
    columns: table => new
    {
        AccountId = table.Column<int>(nullable: false),
        CreatedDateTime = table.Column<DateTime>(nullable: false)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_Account", x => x.AccountId);
        table.ForeignKey(
            name: "FK_Account_User_AccountId",
            column: x => x.AccountId,
            principalTable: "User",
            principalColumn: "UserId",
            onDelete: ReferentialAction.Cascade);
    });

这篇关于流利的Api实体框架核心的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！