Asp.net core中，自带的Log是在当selfhost运行时，在控制台中输出，不便于查阅，如果用一个log架框，把日志持久化，便于查询．
NLog是一个免费的日志记录框架，专门为.net平台下的框架提供日志功能，本文主要说明asp.net core下怎么使用NLog。
首先用Nuget安装NLog.Extensions.Logging和NLog.Web.AspNetCore两个类库。
修改project.json，在publishOptions中添加”nlog.config节点”
"publishOptions": { "include": [ "wwwroot", "**/*.cshtml", "appsettings.json", "web.config", "nlog.config"
]
}
在StartUp.cs中添加
public void ConfigureServices(IServiceCollection services)
{ // Add framework services. services.AddMvc();
//为NLog.web注入HttpContextAccessor
services.AddSingleton();
……
}public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{ //添加NLog到.net core框架中 loggerFactory.AddNLog(); //添加NLog的中间件 app.AddNLogWeb(); //指定NLog的配置文件
env.ConfigureNLog("nlog.config");
……
}
HomeController.
cs中是自定义日志
static Logger Logger = LogManager.GetCurrentClassLogger();public IActionResult Index()
{
Logger.Info("普通信息日志");
Logger.Debug("调试日志");
Logger.Error("错误日志");
Logger.Fatal("异常日志");
Logger.Warn("警告日志");
Logger.Trace("跟踪日志");
Logger.Log(NLog.LogLevel.Warn, "Log日志"); try
{ int i = 0; var a = 10 / i;
} catch (Exception exc)
{ //异常日志 Logger.Fatal(exc, exc.Message);
} return View();
}
NLog.config，有两种日志，记录在C:\temp下，一种是全部日志，一种是自己通过NLog函数记录的日志。如果日志库异常，会产生在c:\temp\internal-nlog.txt下
<?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="Warn"
internalLogFile="c:\temp\internal-nlog.txt">
<add assembly="NLog.Web.AspNetCore"/><target xsi:type="File" name="allfile" fileName="c:\temp\nlog-all-${shortdate}.log"
layout="${longdate}|${event-properties:item=EventId.Id}|${logger}|${uppercase:${level}}|${message} ${exception}" />
<target xsi:type="File" name="ownFile-web" fileName="c:\temp\nlog-own-${shortdate}.log"
layout="${longdate}|${event-properties:item=EventId.Id}|${logger}|${uppercase:${level}}| ${message} ${exception}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}" /><target xsi:type="Null" name="blackhole" /><logger name="*" minlevel="Trace" writeTo="allfile" />
<logger name="Microsoft.*" minlevel="Trace" writeTo="blackhole" final="true" /><logger name="*" minlevel="Trace" writeTo="ownFile-web" />
Layout中$后的数据就是要写日志的内容，关于这些数据可参考https://github.com/nlog/nlog/wiki/Layout-Renderers，可以根据自己的需要，选择要保存的日志数据。
如果想把日志保存到数据库中，可以把NLog.config修改如下：
<?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="Warn"
internalLogFile="c:\temp\internal-nlog.txt">
<add assembly="NLog.Web.AspNetCore"/><target name="database" xsi:type="Database" connectionString="server=.;database=nglogdb;uid=SQL用户名;pwd=SQL密码;">
INSERT INTO [dbo].[NLog] (
[MachineName],
[SiteName],
[Logged],
[Level],
[UserName],
[Message],
[Logger],
[Properties],
[Host],
[Controller],
[Action],
[Url],
[CallSite],
[Exception]
) VALUES (
@machineName,
@siteName,
@logged,
@level,
@userName,
@message,
@logger,
@properties,
@host,
@controller,
@action,
@url,
@callSite,
@exception
); <parameter name="@machineName" layout="${machinename}" /><parameter name="@siteName" layout="${iis-site-name}" /><parameter name="@logged" layout="${date}" /><parameter name="@level" layout="${level}" /><parameter name="@username" layout="${aspnet-user-identity}" /><parameter name="@message" layout="${message}" /><parameter name="@logger" layout="${logger}" /><parameter name="@properties" layout="${all-event-properties:separator=|}" /><parameter name="@host" layout="${aspnet-request-host}" /><parameter name="@controller" layout="${aspnet-MVC-Controller}" /><parameter name="@action" layout="${aspnet-MVC-Action}" /><parameter name="@url" layout="${aspnet-request-url}" /><parameter name="@callSite" layout="${callsite}" /><parameter name="@exception" layout="${exception:tostring}" /><logger name="*" minlevel="Trace" writeTo="database"/>