.Net Core 使用NLog记录日志到文件和数据库

NLog 记录日志是微软官方推荐使用。

接下来，通过配置日志记录到文件和Sql Server数据库。

第一步：首先添加包NLog.Config （可通过微软添加包命令Install-Package 包名进行添加，也可以通过管理NuGet程序包进行添加），添加成功后会生成NLog.config配置文件。并对该配置文件进行配置。详细配置可参考Git上 NLog说明。

一下是我个人配置。

<?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"
      xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd NLog.xsd"
      autoReload="true"
      throwExceptions="false"
      internalLogLevel="Warn"   
      internalLogFile="Logs/nlog-internal.log">
  
  <!--internalLogLevel="Off"-->
  <!-- optional, add some variables
  https://github.com/nlog/NLog/wiki/Configuration-file#variables
  -->
  <variable name="myvar" value="myvalue"/>

  <!--
  See https://github.com/nlog/nlog/wiki/Configuration-file
  for information on customizing logging rules and outputs.
   -->
  <targets>

    <!--
    add your targets here
    See https://github.com/nlog/NLog/wiki/Targets for possible targets.
    See https://github.com/nlog/NLog/wiki/Layout-Renderers for the possible layout renderers.
    -->

    <!--
    Write events to a file with the date in the filename.
    <target xsi:type="File" name="f" fileName="${basedir}/logs/${shortdate}.log"
            layout="${longdate} ${uppercase:${level}} ${message}" />
    -->

    <!-- write logs to file -->
    <target xsi:type="File" name="allfile" fileName="Logs/${date:format=yyyyMM}/nlog-all-${shortdate}.log"
             layout="${longdate}|${event-properties:item=EventId.Id}|${uppercase:${level}}|${logger} ${newline}${message} ${exception} ${newline}" />

    <target xsi:type="File" name="ownFile-web" fileName="Logs/${date:format=yyyyMM}/nlog-own-${shortdate}.log"
             layout="${longdate}|${event-properties:item=EventId.Id}|${uppercase:${level}}|${logger} ${newline}${message} ${exception} ${newline} --- |url: ${aspnet-request-url}|action: ${aspnet-mvc-action}" />

    <target xsi:type="Null" name="blackhole" />

    <target xsi:type="Database" name="database">
      <connectionString>${var:connectionString}</connectionString>
      <commandText>
        insert into syslogs (Application,Levels,Operatingtime,Operatingaddress,Userid,Logger,Callsite,Requesturl,Referrerurl,Action,Message,Exception)
        values (@application,@levels,@operatingtime,@operatingaddress,@userid,@logger,@callSite,@requesturl,@referrerurl,@action,@message,@exception);
      </commandText>
      <parameter name="@application" layout="WebApi" />
      <parameter name="@levels" layout="${level}" />
      <parameter name="@operatingTime" layout="${date}" />
      <parameter name="@operatingaddress" layout="${aspnet-Request-IP}" />
      <parameter name="@userid" layout="1" />
      <parameter name="@logger" layout="${logger}" />
      <parameter name="@callSite" layout="${callsite}" />
      <parameter name="@requesturl" layout="${aspnet-request-url}" />
      <parameter name="@referrerurl" layout="${aspnet-request}" />
      <parameter name="@action" layout="${aspnet-mvc-action}" />
      <parameter name="@message" layout="${message}" />
      <parameter name="@exception" layout="${exception:tostring}" />
    </target>
    
  </targets>

  <rules>
    <!-- add your logging rules here -->

    <!--
    Write all events with minimal level of Debug (So Debug, Info, Warn, Error and Fatal, but not Trace)  to "f"
    <logger name="*" minlevel="Debug" writeTo="f" />
    -->

    <!--All logs, including from Microsoft-->
    <!--minlevel 改为Trace 跟踪全部 Error 只捕获异常-->
    <logger name="*" minlevel="Error" writeTo="allfile" />

    <!--Skip Microsoft logs and so log only own logs-->
    <logger name="Microsoft.*" minlevel="Trace" writeTo="blackhole" final="true" />
    <logger name="*" minlevel="Trace" writeTo="ownFile-web" />
    <logger name="*" minlevel="Trace" writeTo="database" />    
    
  </rules>
</nlog>


<!--增加引用
<PackageReference Include="NLog.Extensions.Logging" Version="1.2.1" />
<PackageReference Include="NLog.Web.AspNetCore" Version="4.6.0" />-->

说明：targets 中有一节点为Database，是配置将日志写入数据库中，注意需要在数据库中添加该记录日志表。

{
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=192.168.30.133;Initial Catalog=Test;User ID=sa;Password=123456;Trusted_Connection=True;MultipleActiveResultSets=true;Integrated Security=false;"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "AllowedHosts": "*"
}

第二步：添加包NLog.Web.AspNetCore，在Program.cs中的WebHost加入".UseNLog()"（该属于程序集NLog.Web，需要添加引用using NLog.Web;）,即为添加nlog.

using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using NLog.Web;

namespace WebApi
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .UseNLog(); //加入nlog日志
    }
}

第三步：在Startup.cs中的Configure方法中添加记日志代码，即需要加载的配置文件和配置日志写入数据库连接字符串代码。注意：为避免中文乱码问题需要添加System.Text.Encoding.CodePages包。

 public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {

            #region Nlog记日志
            //将日志记录到数据库                 config/NLog.config
            NLog.LogManager.LoadConfiguration("nlog.config").GetCurrentClassLogger();       NLog.LogManager.Configuration.Variables["connectionString"] = Configuration.GetConnectionString("DefaultConnection");   Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);  //避免日志中的中文输出乱码
            #endregion

            if (env.IsDevelopment())
                app.UseDeveloperExceptionPage();
            else
                app.UseHsts();
  app.UseHttpsRedirection();

            app.UseMvc();
        }

第四步：使用微软推荐的方式在在构造方法中将将日志对象注入。

 public class UsersController : Controller
    {
        /// <summary>
        /// 日志对象
        /// </summary>
        private readonly ILogger logger;    
         public UsersController(ILoggerFactory loggerFactory)
        {
            this.logger = loggerFactory.CreateLogger<UsersController>();

            #region 测试日志
            logger.LogTrace("开发阶段调试，可能包含敏感程序数据", 1);
            logger.LogDebug("开发阶段短期内比较有用，对调试有益。");
            logger.LogInformation("你访问了首页。跟踪程序的一般流程。");
            logger.LogWarning("警告信息！因程序出现故障或其他不会导致程序停止的流程异常或意外事件。");
            logger.LogError("错误信息。因某些故障停止工作");
            logger.LogCritical("程序或系统崩溃、遇到灾难性故障！！！");
            #endregion
        }

所有工作完成，运行程序。在配置NLog路径下生成日志文件，同时，在数据库中生成日志。