.NET 6 WebAPI：存在appsettings.json时控制器日志无法记录的疑问

DevOps 小满

2026-7-20

问题场景

在.NET 6 WebAPI中，当项目包含如下配置的appsettings.json文件时：

{
  "Logging": {
    "LogLevel": {
      "Default": "Information"
    }
  },
  "AllowedHosts": "*"
}

访问任意端点都不会记录控制器的活动日志，仅输出生命周期相关日志：

info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://localhost:5237
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
      Content root path: C:\Temp\TestApps\Test1\SampleCCLogProviderApp\WebApplication5\WebApplication5\

但删除appsettings.json文件后，就能正常输出所有信息日志，包括控制器的活动日志：

info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://localhost:5237
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
      Content root path: C:\Temp\TestApps\Test1\SampleCCLogProviderApp\WebApplication5\WebApplication5\
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 GET http://localhost:5237/weatherforecast - -
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'WebApplication5.Controllers.WeatherForecastController.Get (WebApplication5)'
info: Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker[3]
      Route matched with {action = "Get", controller = "WeatherForecast"}. Executing controller action with signature System.Collections.Generic.IEnumerable`1[WebApplication5.WeatherForecast] Get() on controller WebApplication5.Controllers.WeatherForecastController (WebApplication5).
info: Microsoft.AspNetCore.Mvc.Infrastructure.ObjectResultExecutor[1]
      Executing ObjectResult, writing value of type 'WebApplication5.WeatherForecast[]'.
info: Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker[2]
      Executed action WebApplication5.Controllers.WeatherForecastController.Get (WebApplication5) in 64.1691ms
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'WebApplication5.Controllers.WeatherForecastController.Get (WebApplication5)'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 GET http://localhost:5237/weatherforecast - - - 200 - application/json;+charset=utf-8 192.2900ms

原因分析

这是.NET 6日志配置的默认逻辑导致的：

当项目没有自定义appsettings.json时，框架会自动加载开发环境的默认日志配置，其中明确将Microsoft.AspNetCore系列命名空间的日志级别设为Information，因此能输出控制器相关的请求日志。
当你添加自定义appsettings.json并仅设置Default日志级别时，会覆盖框架的默认配置。Default仅作用于未明确指定命名空间的日志类别，而控制器活动日志属于Microsoft.AspNetCore、Microsoft.AspNetCore.Mvc等特定命名空间，这些命名空间的日志级别在你的配置中未定义，会默认继承更严格的级别（通常为Warning及以上），所以不会输出Information级别的控制器日志。

解决方案

在appsettings.json的Logging.LogLevel节点中添加Microsoft.AspNetCore命名空间的日志级别配置即可恢复控制器日志输出：

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Information"
    }
  },
  "AllowedHosts": "*"
}

内容的提问来源于stack exchange，提问作者Yogi