c# - EF 核心关系

Question

我在建立人际关系时遇到问题。

我希望每个Post人都有一个 User和许多Comments. 每个User都有很多Comments和Posts（如果我想随时过滤每个用户的评论和帖子）。然后每个Commentto 都有一个 User 和 Post

问题是当我为数据库播种时

if (!ctx.Posts.Any()) {
    Tag tag = new Tag() {
        Name = "Test1"
    };

    User user = new User() {
        UserName = "TestUser",
        Email = "[e-mail]",
        Password = Extensions.PasswordHash("abv123456", config["AppSettings:PasswordSalt"]),
        Role = UserRoles.Member
    };

    ctx.Users.Add(user);

    Post post = new Post() {
        Title = "Test Post",
        Description = "Description post test",
        Likes = 5,
        User = user,
        CreateOn = DateTime.Now,
        LastEditOn = DateTime.Now
    };

    PostTag posttags = new PostTag() {
        Post = post,
        Tag = tag
    };

    ctx.PostTag.Add(posttags);
    ctx.SaveChanges();
};

如果我想获取所有相关的帖子User

public IActionResult GetAllPost() {
    var posts = _ctx.Posts
        .Include(u => u.User)
        .ToList();

    return Json(Newtonsoft.Json.JsonConvert.SerializeObject(posts));
}

我得到Newtonsoft.Json.JsonSerializationException：检测到类型为“Blog.Data.Entities.Post”的自引用循环。路径“[0].User.Posts”。

在我的Configure方法中，我确实忽略了它

services.AddMvc().AddJsonOptions(opts => {
    opts.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
});

OnModelCreating()

protected override void OnModelCreating(ModelBuilder modelBuilder) {
    // set unique email and username
    modelBuilder.Entity<User>()
        .HasIndex(u => new { u.Email, u.UserName })
        .IsUnique();

    // set unique tag name
    modelBuilder.Entity<Tag>()
        .HasIndex(t => t.Name)
        .IsUnique();

    modelBuilder.Entity<Post>()
        .HasOne(p => p.User)
        .WithMany(u => u.Posts);

    modelBuilder.Entity<User>()
        .HasMany(u => u.Comments)
        .WithOne(u => u.User);

    // post tag many-to-many rel
    modelBuilder.Entity<PostTag>()
        .HasKey(pt => new { pt.PostUID, pt.TagUID });

    modelBuilder.Entity<PostTag>()
        .HasOne(pt => pt.Post)
        .WithMany(p => p.PostTags)
        .HasForeignKey(pt => pt.PostUID);

    modelBuilder.Entity<PostTag>()
        .HasOne(pt => pt.Tag)
        .WithMany(p => p.PostTags)
        .HasForeignKey(pt => pt.TagUID);
} 

标签： c#asp.net-coreentity-framework-core

Answer 1

您正在尝试 JSONify 一个 JSON 字符串：

return Json(Newtonsoft.Json.JsonConvert.SerializeObject(posts));

你需要让框架为你做这件事，而不是：

return Json(posts);