Web api使用实体框架从一对多关系仅返回一个子对象 [英] Web Api returns only one child object from one to many relationship using Entity Framework

问题描述

我有一个控制器方法，该方法必须返回带有子代集合的父对象。在调试中，我可以看到在执行过程中有很多子项，但是当我捕获json时，它只有一个子项。

I've got a controller method that must return parent object with collection of children. In debug I can see plenty of children during execution but when I catch a json it has only one child.

    [Route("api/page/{id}")]
    public JsonResult GetPage(int id)
    {
        var item = db.Pages.Include(p => p.PageContainerTemplates)
            .SingleOrDefault(p => p.Id == id);
        return Json(item);
    }

我有很多孩子，而Entity Framework Core却得到了所有，但响应为json看起来像这样：

I've got many children and Entity Framework Core get them all but response json looks like this:

{
  "name": "Index",
  "bodyClasses": "full-width-container transparent-header",
  "title": "Index",
  "pageContainerTemplates": [
    {
      "position": 8,
      "pageId": 1
    }
  ]
}

父母对象看起来像这样：

Parent object looks like this:

public class Page : BaseEntity
{
    public string Name { get; set; }
    public string BodyClasses { get; set; }
    public string Title { get; set; }
    public virtual List<PageContainerTemplate> PageContainerTemplates { get; set; } 
}

孩子看起来像这样：

public class PageContainerTemplate : BaseEntity
{
    public int Position { get; set; }
    public int PageId { get; set; }
    public Page Page { get; set; }
    public int ContainerTemplateId { get; set; }
    public ContainerTemplate ContainerTemplate { get; set; }
}

我没有任何其他关系或任何其他键，但是什么是奇怪的是，我在JSON中的独生子没有 containerTemplateId属性

I haven't got any additional relationships or any alternative keys but what is strange is than my only child in json haven't got a "containerTemplateId" attribute

推荐答案

尝试一下：

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

已对问题进行了讨论 https://github.com/aspnet/Mvc/issues/4160 和 https://github.com/aspnet/EntityFramework/issues/4646 另请参见循环引用

The issue was discussed https://github.com/aspnet/Mvc/issues/4160 and https://github.com/aspnet/EntityFramework/issues/4646 also see circular reference

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