此筆記記載了本人在.Net Core 5.0環境下生成Json資料時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.的症狀、排查及解決方案。

環境

.Net Core版本：5.0

編譯器：Visual Studio 2019，Rider2021.1.3

症狀

在生成Json資料的時候會提示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.

解決方案

造成此問題的原因是由於在生成Json物件的時候屬性的迴圈引用導致的。

可用如下方法進行解決

1. 安裝 Microsoft.AspNetCore.Mvc.NewtonsoftJson 包

   可以從Nuget上進行下載並安裝

2. 安裝完成後在 Startup.cs 檔案中加入如下程式碼

   public void ConfigureServices(IServiceCollection services)
   {
       // .Net Core 5.0以下適用
       services.AddMvc(options => { options.Filters.Add<ApiModelCheckFilterAttribute>(); })
           .AddJsonOptions(options =>
           {
               // 忽略屬性的迴圈引用
           	options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
           });
       
       // .Net Core 5.0適用
       services.AddMvc(options => { options.Filters.Add<ApiModelCheckFilterAttribute>(); })
           .AddNewtonsoftJson(options =>
           {
               // 忽略屬性的迴圈引用
           	options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
           });
   }