.net core使用NLog记录

 首先使用Nugut安装NLog, NLog.Extensions.Logging,using NLog.Web，并且加上配置文件 ”nlog.config“,配置文件内容网上都可以百度的到。这是我自己的：

创建表：

CREATE TABLE `sys_log` (
`Id` int(11) NOT NULL AUTO_INCREMENT,
`Account` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`ActionType` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`Level` varchar(5) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`Message` longtext CHARACTER SET utf8 COLLATE utf8_general_ci NULL,
`Date` datetime(0) NULL DEFAULT NULL,
PRIMARY KEY (`Id`) USING BTREE,
UNIQUE INDEX `Id_UNIQUE`(`Id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 11 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

  配置config文件

<?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="true"
internalLogLevel="Off" internalLogFile="c: emp log-internal.log">

<!-- optional, add some variables
https://github.com/nlog/NLog/wiki/Configuration-file#variables
-->
<variable name="myvar" value="myvalue"/>

<!--
-->
<targets>
<target name="console" xsi:type ="Console" />
<target name="debugger" xsi:type="Debugger" layout="${date:format=HH:mm:ss.fff}: ${message}" />
<target name="error_file" xsi:type="File"
fileName="${basedir}/Logs/Error/${shortdate}/error.txt" maxArchiveFiles="30"
layout="${longdate} | ${level:uppercase=false} | ${message} ${onexception:${exception:format=tostring} ${newline} ${stacktrace} ${newline}" />
<target name="info" xsi:type="File"
fileName="${basedir}/Logs/Info/${shortdate}/info.txt" maxArchiveFiles="30"
layout="${longdate} | ${level:uppercase=false} | ${message} ${onexception:${exception:format=tostring} ${newline} ${stacktrace} ${newline}" />
<target name="database" xsi:type="Database">
<connectionString>${var:ConnectionStrings}</connectionString>
<commandText>
INSERT INTO lifeHome.sys_log (Account,ActionType,Level,Message,Date) Values(@Account,@ActionType,@Level,@Message,@Date)
</commandText>
<parameter name = "@Account" layout = "${event-context:item=Account}"/>
<parameter name = "@ActionType" layout = "${event-context:item=ActionType}"/>
<parameter name = "@Level" layout = "${event-context:item=Level}" />
<parameter name = "@Message" layout = "${event-context:item=Message}" />
<parameter name = "@Date" layout = "${event-context:item=Date}" />
<dbProvider>MySql.Data.MySqlClient.MySqlConnection,Mysql.Data</dbProvider>
</target>
</targets>
<rules>
<logger name="*" writeTo="console" />
<logger name="*" minlevel="Debug" writeTo="debugger" />
<logger name="*" minlevel="Error" writeTo="error_file" />
<logger name="*" level="Info" writeTo="info" />
<logger name="*" writeTo="database" />
</rules>
</nlog>

 因为之前一直无法将日志写入数据库，于是百度了好久，将”throwExceptions“设置为true，部署在生产环境建议改为false，这样就可以调试看到错误了，我的原因是sql错误。

  <connectionString>此处是为了灵活配置sql连接。

 之后在Startup.cs里面加上如下代码：

public void Configure(IApplicationBuilder app, IHostingEnvironment env,ILoggerFactory loggerFactory)
{

         //加载Nlog
         loggerFactory.AddNLog();

         //加载配置文件
         env.ConfigureNLog("nlog.config");

         //读取数据库连接
         NLog.LogManager.Configuration.Variables["ConnectionStrings"]=_configuration.GetConnectionString("connection");

      );
   });
}

然后在Program.cs里面写上

public static IWebHost BuildWebHost(string[] args) =>
   WebHost.CreateDefaultBuilder(args)
    .UseStartup<Startup>().UseNLog()
.       Build();

然后使用过滤器

  

/// <summary>
/// 全局异常过滤
/// </summary>
public class ExceptionFilter : Attribute,IExceptionFilter
{
     private readonly ILogger logger;
     public ExceptionFilter()
     {
          logger = LogManager.GetCurrentClassLogger();
      }
      public void OnException(ExceptionContext context)
      {

       //如果异常未处理
     if(context.ExceptionHandled==false)
       {
          LogEventInfo lei = new LogEventInfo();
          lei.Level = LogLevel.Error;
          lei.Properties["Account"] = "1";
          lei.Properties["Date"] =DateTime.Now;
          lei.Properties["ActionType"] = "1";
          lei.Properties["Level"] = "1";
          lei.Properties["Message"] = "1";
          logger.Log(lei);
          //异常已处理
         context.ExceptionHandled = true;
    }
   }
}

 数据可以记录到数据库，但是使用简单写法如： logger.Error("12344")还未成功