在ASP.NET Core 6.0中，官方提供了内置日志记录提供程序,如:

控制台-提供程序将输出记录到控制台
EventLog-提供程序将日志输出发送到 Windows 事件日志
…

除了内置日志功能外，也有很多第三方日志记录提供程序,这里列举几个比较热门的日志组件:

Log4Net-(Github)[https://github.com/huorswords/Microsoft.Extensions.Logging.Log4Net.AspNetCore]
NLog-(Github)[https://github.com/NLog/NLog.Extensions.Logging]
Serilog-(Github)[https://github.com/serilog/serilog-aspnetcore]
Sentry-(Github)[https://github.com/getsentry/sentry-dotnet]

接下来，我们便学习如何在程序里使用这些组件

Log4Net

安装Log4Net包

创建配置文件

新建一个名为log4net.config的配置文件

加入配置

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
    <appender name="Console" type="log4net.Appender.ConsoleAppender">
        <layout type="log4net.Layout.PatternLayout">
            <!-- Pattern to output the caller's file name and line number -->
            <conversionPattern value="%date %5level %logger.%method [%line] - MESSAGE: %message%newline %exception" />
        </layout>
    </appender>
    <appender name="RollingFile" type="log4net.Appender.RollingFileAppender">
        <file value="example.log" />
        <appendToFile value="true" />
        <maximumFileSize value="100KB" />
        <maxSizeRollBackups value="2" />
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date %5level %logger.%method [%line] - MESSAGE: %message%newline %exception" />
        </layout>
    </appender>
    <appender name="TraceAppender" type="log4net.Appender.TraceAppender">
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date %5level %logger.%method [%line] - MESSAGE: %message%newline %exception" />
        </layout>
    </appender>
    <appender name="ConsoleAppender" type="log4net.Appender.ManagedColoredConsoleAppender">
        <mapping>
            <level value="ERROR" />
            <foreColor value="Red" />
        </mapping>
        <mapping>
            <level value="WARN" />
            <foreColor value="Yellow" />
        </mapping>
        <mapping>
            <level value="INFO" />
            <foreColor value="White" />
        </mapping>
        <mapping>
            <level value="DEBUG" />
            <foreColor value="Green" />
        </mapping>
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date %5level %logger.%method [%line] - MESSAGE: %message%newline %exception" />
        </layout>
    </appender>
    <root>
        <level value="TRACE" />
        <appender-ref ref="RollingFile" />
        <appender-ref ref="TraceAppender" />
        <appender-ref ref="ConsoleAppender" />
    </root>
</log4net>

使用Log4Net

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builder.Logging.ClearProviders();
builder.Logging.AddLog4Net();

然后在需要记录日志的地方引入，使用ILogger，这里我依然以OrderController为例

private readonly ILogger<OrdersController> _logger;

       public OrdersController(DemoContext context, ILogger<OrdersController> logger)
       {
           _context = context;
           _logger = logger;
       }

当我们访问该接口后，会在控制台打印出相关信息

亦会在运行目录下生成名为example.log的日志文件

NLog

安装NLog

创建配置文件

新建一个名为nlog.config的配置文件，并加入如下配置

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      autoReload="true"
      internalLogLevel="Info"
      throwConfigExceptions="true"
      internalLogFile="c:tempinternal-nlog-AspNetCore6.txt">

  <!-- enable asp.net core layout renderers -->
  <extensions>
    <add assembly="NLog.Web.AspNetCore"/>
  </extensions>

  <!-- the targets to write to -->
  <targets>
    <!-- File Target for all log messages with basic details -->
    <target xsi:type="File" name="allfile" fileName="c:tempnlog-AspNetCore6-all-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}" />

    <!-- File Target for own log messages with extra web details using some ASP.NET core renderers -->
    <target xsi:type="File" name="ownFile-web" fileName="c:tempnlog-AspNetCore6-own-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}|${callsite}| body: ${aspnet-request-posted-body}" />

    <!--Console Target for hosting lifetime messages to improve Docker / Visual Studio startup detection -->
    <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" />
  </targets>

  <!-- rules to map from logger name to target -->
  <rules>
    <!--All logs, including from Microsoft-->
    <logger name="*" minlevel="Trace" writeTo="allfile" />

    <!--Output hosting lifetime messages to console target for faster startup detection -->
    <logger name="Microsoft.Hosting.Lifetime" minlevel="Info" writeTo="lifetimeConsole, ownFile-web" final="true" />

    <!--Skip non-critical Microsoft logs and so log only own logs (BlackHole) -->
    <logger name="Microsoft.*" maxlevel="Info" final="true" />
    <logger name="System.Net.Http.*" maxlevel="Info" final="true" />

    <logger name="*" minlevel="Trace" writeTo="ownFile-web" />
  </rules>
</nlog>

使用NLog

在Program.cs加入如下代码，

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builder.Logging.ClearProviders();
builder.Logging.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);  //日志级别
builder.Host.UseNLog();

日志是使用方式不变，因为是直接替换的日志的组件，基于接口的日志调用方式不变。

Serilog

安装Serilog

使用Serilog

这里为了演示，我就偷个懒，直接将信息写在代码中,先是配置日志规则

Log.Logger = new LoggerConfiguration()
    .WriteTo.Console()
    .WriteTo.File("log-.txt", rollingInterval: RollingInterval.Day, outputTemplate: "{Timestamp:HH:mm} [{Level}] ({ThreadId}) {Message}{NewLine}{Exception}")
    .CreateLogger();

然后在使用Serilog