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

问题描述

我有两个一对多的实体

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;}
}

如果我尝试使用我的 api 预订餐厅

If I try to get restaurants with reservations using my api

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

我收到错误响应，因为对象包含彼此的引用.有相关帖子推荐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，第二个建议没有帮助.有没有办法在没有循环关系的情况下加载数据?*

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:检测到可能的对象循环不支持.这可能是由于周期或如果对象深度大于最大允许深度 32.System.Text.Json.ThrowHelper.ThrowInvalidOperationException_SerializerCycleDetected(Int32maxDepth) 在 System.Text.Json.JsonSerializer.Write(Utf8JsonWriterwriter, Int32 originalWriterDepth, Int32 flushThreshold,JsonSerializerOptions 选项，WriteStack&状态)在System.Text.Json.JsonSerializer.WriteAsyncCore(Stream utf8Json, Object值，输入类型，JsonSerializerOptions 选项，CancellationToken 取消令牌)在Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext上下文，Encoding selectedEncoding) 在Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext上下文，Encoding selectedEncoding) 在Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker调用者、任务上一个任务、下一个状态、作用域范围、对象状态、布尔值已完成)在Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed上下文)在Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State&接下来，范围&范围、对象&状态，布尔&已完成)在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

我在一个新项目中尝试了你的代码，安装包后第二种方法似乎运行良好 Microsoft.AspNetCore.Mvc.NewtonsoftJson 首先用于 3.0

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
);

尝试新项目并比较差异.

Try with a new project and compare the differences.

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