EFCore - 如何將多個導航屬性設置為相同類型？

Question

我的模型包含Post和PostHistory類，其中Post與PostHistory有一對多的關系。

class Post
{
    public int Id { get; set; }

    public PostVersion CurrentVersion { get; set; }
    public PostVersion OriginalVersion { get; set; }
    public IList<PostVersion> History { get; set; }
}

class PostVersion
{
    public int Id { get; set; }
    public Post Post { get; set; }

    public string Title { get; set; }
    public string Body { get; set; }
}

History屬性包含與該Post相關的所有PostVersions的列表。 CurrentVersion和PreviousVersion屬性都引用該帖子歷史記錄中的特定版本（最新版本和最新版本）。

我的問題是EF Core很難理解由於CurrentVersion和OriginalVersion導航屬性導致的關系。 當我嘗試創建遷移時，我收到以下錯誤消息：

Unable to determine the relationship represented by navigation property 'Post.CurrentVersion' of type 'PostVersion'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.

之后，我嘗試使用Fluent API手動創建關系。

protected override void OnModelCreating(ModelBuilder builder)
{
    base.OnModelCreating(builder);

    builder.Entity<Post>()
        .HasMany(x => x.History)
        .WithOne(x => x.Post);
    builder.Entity<Post>()
        .HasOne(x => x.CurrentVersion)
        .WithOne(x => x.Post);
    builder.Entity<Post>()
        .HasOne(x => x.OriginalVersion)
        .WithOne(x => x.Post);
}

但創造了一個不同的錯誤：

Cannot create a relationship between 'PostVersion.Post' and 'Post.CurrentVersion', because there already is a relationship between 'Post.History' and 'PostVersion.Post'. Navigation properties can only participate in a single relationship.

是否有可能在EF Core代碼中首先創建這種關系？

Answer 1

編輯我做了一些更改，你不能在多個關系中引用相同的屬性。 因此我不得不使用外鍵進行映射。 PostVersion只有你需要的一個Post引用。

public class Post
{
    public Guid Id { get; set; }

    public Guid CurrentVersionId { get; set; }
    public PostVersion CurrentVersion { get; set; }
    public Guid OriginalVersionId { get; set; }
    public PostVersion OriginalVersion { get; set; }
    public IList<PostVersion> History { get; set; }
}

public class PostVersion
{
    public Guid Id { get; set; }
    public Guid PostId { get; set; }

    public Post Post { get; set; }

    public string Title { get; set; }
    public string Body { get; set; }
}

modelBuilder.Entity<Post>()
    .HasOne(x => x.CurrentVersion)
    .WithOne()
    .HasForeignKey<Post>(p => p.CurrentVersionId);
modelBuilder.Entity<Post>()
    .HasOne(x => x.OriginalVersion)
    .WithOne()
    .HasForeignKey<Post>(p => p.OriginalVersionId);

modelBuilder.Entity<Post>()
    .HasMany(x => x.History)
    .WithOne(p => p.Post)
    .HasForeignKey(pv => pv.PostId);

---

原始您需要為第二個關系指定其他屬性

public class Post
{
    public Guid Id { get; set; }

    public PostVersion CurrentVersion { get; set; }
    public PostVersion OriginalVersion { get; set; }
    public IList<PostVersion> History { get; set; }
}

public class PostVersion
{
    public Guid Id { get; set; }
    public Post Post { get; set; }
    public Post SecondPost { get; set; }
    public Post ThirdPost { get; set; }

    public string Title { get; set; }
    public string Body { get; set; }
}


 modelBuilder.Entity<Post>()
            .HasOne(x => x.CurrentVersion)
            .WithOne(x => x.Post);
 modelBuilder.Entity<Post>()
            .HasOne(x => x.OriginalVersion)
            .WithOne(x => x.SecondPost);
 modelBuilder.Entity<Post>()
            .HasMany(x => x.History)
            .WithOne(x => x.ThirdPost);