问题描述
我遇到了错误:
JsonSerializationException:检测到自引用循环属性主题"，类型为Project.Models.Subject".小路'数据[0].总计'.
JsonSerializationException: Self referencing loop detected for property 'Subject' with type 'Project.Models.Subject'. Path 'data[0].Totals'.
当我使用由 IEnumerable<Subject> 模型填充的 dataGrid 加载视图时，会发生这种情况.Grid 是一个 DevExtreme DataGrid 绑定到 View 的模型，如下所示:
It occurs when I load a View with a dataGrid populated by an IEnumerable<Subject> model. The Grid is a DevExtreme DataGrid bound to the View's model like this:
@(Html.DevExtreme().DataGrid()
.DataSource(Model)
.Paging(paging =>
{
paging.Enabled(true);
paging.PageIndex(0);
paging.PageSize(20);
})
.Columns(columns =>
{
columns.Add().DataField("SubjectId");
... other fields
})
)
从使用此功能从存储库中提取数据的控制器填充:
Which is populated from a Controller that pulls data from a Repository with this function:
public async Task<IEnumerable<Subject>> GetSubjectsAsync()
{
return await _context.Subject.ToListAsync();
}
Subject 表与 Totals 具有 1:1 的关系，其中 Totals 具有对 Subject 的外键引用.项目中的模型如下所示(由 Scaffold-DbContext 生成):
The Subject table has a 1:1 relationship with Totals with Totals having a foreign key reference to Subject. The Models in the project look like this (generated from Scaffold-DbContext):
public partial class Subject
{
public Guid SubjectId { get; set; }
public virtual Totals Totals { get; set; }
}
public partial class Totals
{
public Guid TotalsId { get; set; }
public virtual Subject Subject { get; set; }
}
由于 2 个对象相互引用，因此在序列化时会导致循环.为了纠正这个问题，我将此配置添加到我的 Startup.ConfigureServices 方法中:
Since the 2 objects reference eachother it causes a loop when serializing it. To correct this I added this config to my Startup.ConfigureServices method:
services.AddMvc()
.AddJsonOptions(x => x.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore);
我从这个答案中得到:https://stackoverflow.com/a/40501464/7897176
但是，这并不能解决问题，当我加载涉及主题的视图时，它仍然会导致错误.将 [JsonIgnore] 添加到 Totals 的 Subject 属性可以解决问题，但是我不想将其添加到模型中的每个子属性中，并且每当我更新模型时都必须重做数据库.
However this doesn't fix the problem and its still causing an error when I load a view that involves Subjects. Adding [JsonIgnore] to the Subject property of Totals fixes the problem, but I don't want to have to add that to every child property in my models and have to redo it whenever I update my models from the db.
推荐答案
JSON序列化时自引用循环的问题与EFCore如何加载相关数据有关(docs).加载集合时，相关实体可能会自动填充，也可能不会自动填充，具体取决于先前是否已加载这些对象.它被称为导航属性的自动修复.或者，可以通过 .Include().
The problem of self-referencing loops during JSON serialization is connected to how EFCore loads related data (docs). When you load a collection, related entities may or may not be automatically populated depending on whether or not those object have been previously loaded. It's called automatic fix-up of navigation properties. Alternatively, they may be eagerly loaded via .Include().
当您获得要序列化的实体的自引用图时，有多种选择:
Whenever you get a self-referencing graph of entities to be serialized, there are several options:
Newtonsoft.Json.ReferenceLoopHandling.Ignore(官方推荐).它可以工作，但如果自引用发生在层次结构的深处，仍然会导致序列化过多的数据.
Newtonsoft.Json.ReferenceLoopHandling.Ignore(officially recommended). It works but still can result in serializing excessive data if self-reference occurs deep in the hierarchy.
[JsonIgnore] 属性.正如您所指出的，重新生成模型类时属性会消失.因此，它们的使用可能会很不方便.
[JsonIgnore] attribute on navigation properties. As you noted, attributes disappear when model classes are regenerated. Thus, their use can be inconvenient.
(最佳选择)预选属性子集:
var minimallyNecessarySet= _nwind.Products.Select(p => new {
p.ProductID,
p.ProductName,
p.UnitPrice,
p.CategoryID
});
return minimallyNecessarySet.ToList();
这种方法的优点是只序列化所需的数据.它与 DevExtreme 的 DataSourceLoader 兼容:
This approach has the advantage of serializing only required data. It's compatible with DevExtreme's DataSourceLoader:
return DataSourceLoader.Load(minimallyNecessarySet, loadOptions);
这篇关于使用 Entity Framework Core 的 Newtonsoft JsonSerializer 的自引用循环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编程学习网！