检测到不支持的.Net Core 3.0可能的对象周期 [英] .Net Core 3.0 possible object cycle was detected which is not supported

问题描述

我有2个相互关联的实体

I have 2 entities that are related as one to many

public class Restaurant {
   public int RestaurantId {get;set;}
   public string Name {get;set;}
   public List<Reservation> Reservations {get;set;}
   ...
}

public class Reservation{
   public int ReservationId {get;set;}
   public int RestaurantId {get;set;}
   public Restaurant Restaurant {get;set;}
}

如果我尝试使用自己的api获取预订的餐厅

If I try to get restaurants with reservations using my api

   var restaurants =  await _dbContext.Restaurants
                .AsNoTracking()
                .AsQueryable()
                .Include(m => m.Reservations).ToListAsync();
    .....

由于对象包含彼此的引用，因此我收到错误消息. 有相关的帖子建议创建单独的模型 或添加 NewtonsoftJson配置

I receive error in response, because objects contain references to each other. There are related posts that recommend to create separate model or add NewtonsoftJson configuration

问题是我不想创建单独的模型，第二个建议也无济于事. 有没有没有循环关系的加载数据的方法吗? *

Problem is that I do not want to create separate model and 2nd suggestion didn't help. Is there any way to load data without cycled relationship ? *

System.Text.Json.JsonException:检测到可能的对象周期 不支持.这可能是由于周期造成的，也可能是由于 对象深度大于最大允许深度32. System.Text.Json.ThrowHelper.ThrowInvalidOperationException_SerializerCycleDetected(Int32 maxDepth)位于System.Text.Json.JsonSerializer.Write(Utf8JsonWriter writer，Int32 originalWriterDepth，Int32 flushThreshold， JsonSerializerOptions选项，WriteStack&州) System.Text.Json.JsonSerializer.WriteAsyncCore(Stream utf8Json，Object 值，类型inputType，JsonSerializerOptions选项， 的CancellationToken cancelToken() Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext 上下文，编码selected(Encoding) Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext 上下文，编码selected(Encoding) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited | 29_0 [TFilter，TFilterAsync](ResourceInvoker 调用程序，任务lastTask，状态下一个，作用域范围，对象状态，布尔值 isCompleted) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed 上下文) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext [TFilter，TFilterAsync](状态 接下来，Scope&范围，对象与对象状态，布尔值和isCompleted) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()

System.Text.Json.JsonException: A possible object cycle was detected which is not supported. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32. at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_SerializerCycleDetected(Int32 maxDepth) at System.Text.Json.JsonSerializer.Write(Utf8JsonWriter writer, Int32 originalWriterDepth, Int32 flushThreshold, JsonSerializerOptions options, WriteStack& state) at System.Text.Json.JsonSerializer.WriteAsyncCore(Stream utf8Json, Object value, Type inputType, JsonSerializerOptions options, CancellationToken cancellationToken) at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding) at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()

*

推荐答案

我已经在一个新项目中尝试了您的代码，安装软件包

I have tried your code in a new project and the second way seems to work well after installing the package Microsoft.AspNetCore.Mvc.NewtonsoftJson firstly for 3.0

services.AddControllersWithViews()
    .AddNewtonsoftJson(options =>
    options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
);

尝试一个新项目并比较差异.

Try with a new project and compare the differences.

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