安置　　Microsoft.AspNetCore.Mvc.Newtonsoft　　包

在startup.cs中添加

public void ConfigureServices(IServiceCollection services) { services.AddControllers(); services.AddMvcCore().AddNewtonsoftJson(options => { options.SerializerSettings.DateFormatString = "yyyy-MM-dd HH:mm:ss"; }); RegisterMyServices(services); }

netcore 3.1 This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32.