EF Core创建多个外键列 [英] EF Core creates multiple foreign key columns

问题描述

我将EF Core与.Net Core 3.1一起使用

Im using EF Core with .Net Core 3.1

我有一个简单的Client-Event关系示例：

I have simple example of Client-Event relationship:

public class BaseEntity
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public DateTime CreatedOn { get; set; }
    public DateTime? ModifiedOn { get; set; }

}

public class Client : BaseEntity
{

    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    public string Phone { get; set; }

}

public class Event : BaseEntity
{

    public DateTime Start { get; set; }
    public DateTime End { get; set; }
    public Client Client { get; set; }
}

在我的上下文中，我使用 FluentAPI 指定关系：

In my context, im using FluentAPI to specify relationships:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{

    modelBuilder.Entity<Event>()
        .HasOne<Client>()
        .WithMany()
        .IsRequired()
        .OnDelete(DeleteBehavior.Cascade);

}

创建迁移时，Client Table看起来不错，但是事件表如下所示：

When I create migration, the Client Table looks fine, but Event table looks like this:

migrationBuilder.CreateTable(
            name: "Events",
            columns: table => new
            {
                Id = table.Column<int>(nullable: false)
                    .Annotation("SqlServer:Identity", "1, 1"),
                CreatedOn = table.Column<DateTime>(nullable: false),
                ModifiedOn = table.Column<DateTime>(nullable: true),
                Start = table.Column<DateTime>(nullable: false),
                End = table.Column<DateTime>(nullable: false),
                ClientId = table.Column<int>(nullable: false),
                ClientId1 = table.Column<int>(nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_Events", x => x.Id);
                table.ForeignKey(
                    name: "FK_Events_Clients_ClientId",
                    column: x => x.ClientId,
                    principalTable: "Clients",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
                table.ForeignKey(
                    name: "FK_Events_Clients_ClientId1",
                    column: x => x.ClientId1,
                    principalTable: "Clients",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

最后，我最终得到了两列： ClientId 和 ClientId1 。为什么EntifyFramework为我的关系创建两列？

Finally I end up having two columns: ClientId and ClientId1. Why is EntifyFramework creating two columns for my relationship?

到目前为止，我还没有使用FluentApi，它与影子属性ClientId自动生成的效果很好，但是我需要从该实体配置级联删除，并且由于没有另一种方式，我指定了上图所示的关系。从那时起，还有一个外键列。

I wasnt using FluentApi so far and it worked perfectly with just shadow property ClientId auto-generated, but i needed to configure cascade delete form this entities, and since there is no other way to do it, I specified the relationship as pictured above. Since then, there is additional foreign key column for it.

我尝试查看外键列：

modelBuilder.Entity<Event>()
            .HasOne<Client>()
            .WithMany()
            .IsRequired()
            .HasForeignKey("ClientId")
            .OnDelete(DeleteBehavior.Cascade);

到目前为止没有效果。有没有办法使用自动生成的阴影属性告诉EF im？

No effect so far. Is there any way to tell EF im using auto generated shadow properties?

编辑＃1：

我也尝试像我自己那样自己查看外键属性：

I also tried specyfing Foreign keys properties on my own like this:

public class Event : BaseEntity
{

    public DateTime Start { get; set; }
    public DateTime End { get; set; }
    public int ClientId { get; set; }
    public Client Client { get; set; }
}

然后

modelBuilder.Entity<Event>()
    .HasOne<Client>()
    .WithMany()
    .IsRequired()
    .HasForeignKey(e => e.ClientId)
    .OnDelete(DeleteBehavior.Cascade);

但仍然没有效果。

推荐答案

事实证明，关系可能是空的-决定权由框架决定，但这并不能真正满足您的兴趣。我修改了代码，因此显式指向了导航属性，EF识别出该关系并停止为列创建阴影属性：

It turns out, relationships can be empty - leaving decision to the framework, but it doesn't really serve Your interest. I modified my code, so there is explicit pointing at the navigation property, and EF recognized the relationship and stopped creating shadow properties for the columns:

modelBuilder.Entity<Event>()
    .HasOne<Client>(e => e.Client)
    .WithMany()
    .IsRequired()
    .OnDelete(DeleteBehavior.Cascade);

这篇关于EF Core创建多个外键列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！