.Net学习——Nlog日志框架的使用

1什么是Nlog，为什么要使用Nlog作为日志框架

.Net没有内置的文本日志提供者，对于实际需要记录日志到文本文件中的需求不相匹配，常用的第三方日志框架包括Log4Net，Nlog,SeriLog。考虑到系统的兼容性与使用的简易程度，推荐使用NLog框架记录系统运行日志记录。
NLog是一个灵活且免费的日志记录平台，适用于各种.NET平台，包括.NET标准。 NLog 使写入多个目标变得容易。（数据库、文件、控制台，调试输出，电子邮件，时间日志）并动态更改日志记录配置。

易于配置
NLog 非常容易配置，无论是通过配置文件还是以编程方式。即使不重新启动应用程序，也可以更改配置。
可模板化
每个日志消息都可以使用各种布局渲染进行模板化
扩展
NLog 已经包含多个目标和预定义布局，但您也可以扩展使用您自己的自定义目标和布局，或包含自己的自定义上下文值
结构化日志记录
完全支持结构化日志记录和处理消息模板和自定义日志事件属性。
微软扩展日志记录
NLog可以与MicrosoftExtensible Logging（和 ASP.NET Core）完全集成，而无需替换标准的Microsoft LoggerFactory。 NLog 自动捕获LogEvent 属性，并可以在结构化日志记录目标输出中使用它们。
appsettings.json
NLog 配置可以从appsettings.json加载，作为NLog.configXML 文件的替代方法。这也是可能的使用 appsettings.json 中的值配置 NLog 目标，with${configset}

2 Nlog.config配置文件

日志输出的位置，布局及样式设置均是可以自行配置的，通常使用Nlog.config这个xml配置文件。该配置文件可以在多个位置下，以扫描到的第一个Nlog.config的规则为准，若启动项未扫描到Nlog.config，则log规则不生效。

2.1 Nlog.config加载位置

对于独立的 *.exe 应用程序，按如下方式搜索文件：

标准应用程序配置文件 app.config（例如应用程序名称.exe.config）
应用程序目录中的应用程序名称.exe.nlog
应用程序目录中的 NLog.config
NLog.dll.nlog 位于 NLog.dll 所在的目录中（仅当 GAC 中未安装 NLog时）

对于 ASP.NET 应用程序，按如下方式搜索文件：

标准 Web 应用程序配置文件 Web.config
web.nlog 位于与 web.config 相同的目录中
应用程序目录中的NLog.config
NLog.dll.nlog 位于 NLog.dll 所在的目录中（仅当 GAC 中未安装 NLog 时）

2.2 Nlog.config.xml

nlog配置文件官方文档说明

<?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"internalLogFile="./logs/internal-nlog-AspNetCore.txt">  <!-- 日志输出目录 相对路径与绝对路径 --><!-- enable asp.net core layout renderers --><extensions><add assembly="NLog.Web.AspNetCore"/></extensions><!-- targets标签定义日志输出目标，由多个target标签来定义 --><targets><!-- type: type=File输出类型为文件 fileName:fileName日志文件名 layout:记录日志文件的格式信息 layout的具体样式与配置layoutrenders有关,定制化不同的layout可参考官方文档的layoutrenders信息--> <!-- longdate:日期 格式形如`yyyy-MM-dd HH:mm:ss.ffff`--> <!-- target xsi:type="File" 时，其他的标签属性可以看配置文档 https://github.com/NLog/NLog/wiki/File-target--> <target xsi:type="File" name="allfile" fileName="./logs/nlog-AspNetCore-all-${shortdate}.log"layout="${longdate}|${event-properties:item=EventId:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}" /><!-- target记录的最大日志大小，单位为字节  archiveAboveSize:单个日志最大保存的日志大小，单位是字节  maxArchiveFiles :指定日志保存的最大个数--><target xsi:type="File" name="ownFile-web" fileName="./logs/nlog-AspNetCore-own-${shortdate}.log"archiveAboveSize ="10000" maxArchiveFiles="3"layout="${longdate}|${event-properties:item=EventId:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}|${callsite}" /><!--Console Target for hosting lifetime messages to improve Docker / Visual Studio startup detection --><!-- target xsi:type="Console" 时，其他的标签属性可以看配置文档 https://github.com/NLog/NLog/wiki/Console-target--> <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" /></targets><!-- rules标签定义每个target的输出规则 一个target标签可以对应多个输出规则，从上往下进行规则的匹配--><rules><!--name:实际日志的名字，通常是命名空间加ILogger<T>的T信息 minlevel:记录Trace级别以上的日志信息，会根据名叫allfile的target定义的日志输出信息规则进行日志记录--><logger name="*" minlevel="Trace" writeTo="allfile" /><!--final:final=true时，尽管日志往下可能还有多个规则与该日志记录匹配，也不会再往下进行target与rule关系的映射了 --><logger name="Log.Service" minlevel="Info" writeTo="lifetimeConsole" final="true" /><!--maxlevel：日志记录的最大级别，maxlevel=Info 记录Info级别以下的资源--><logger name="Log.*" maxlevel="Info" final="true" /><logger name="Log1.*" minlevel="Trace" writeTo="ownFile-web" /><logger name="System.Net.Http.*" maxlevel="Info" final="true" /></rules>
</nlog>

该配置文件属性：Copy If newer

3 使用步骤【.NetCore项目结构】

安装Nlog的nuge包
SDK2.1版本时安装 NLog.Extensions.Logging, Version=5.0.0.0
注入Nlog服务

startup类中修改ConfigureServices（IServiceCollection services）方法

public void  ConfigureServices(IServiceCollection services){//添加Nlog服务services.AddLogging(loggingbuilder=> {loggingbuilder.AddNLog();});}

配置Log文件的输出规则

Nlog.config.xml配置文件进行配置，具体xml的内容需要根据实际业务进行编写。nlog配置文件官方文档说明

注入logger，记录日志信息
利用构造函数注入 private readonly ILogger<泛型> logger；调用扩展方法记录日志

  //// 摘要://     Formats the message and creates a scope.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to create the scope in.////   messageFormat://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.//// 傳回://     A disposable scope object. Can be null.public static IDisposable BeginScope(this ILogger logger, string messageFormat, params object[] args);//// 摘要://     Formats and writes a log message at the specified log level.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   logLevel://     Entry will be written on this level.////   exception://     The exception to log.////   message://     Format string of the log message.////   args://     An object array that contains zero or more objects to format.public static void Log(this ILogger logger, LogLevel logLevel, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a log message at the specified log level.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   logLevel://     Entry will be written on this level.////   eventId://     The event id associated with the log.////   message://     Format string of the log message.////   args://     An object array that contains zero or more objects to format.public static void Log(this ILogger logger, LogLevel logLevel, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes a log message at the specified log level.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   logLevel://     Entry will be written on this level.////   message://     Format string of the log message.////   args://     An object array that contains zero or more objects to format.public static void Log(this ILogger logger, LogLevel logLevel, string message, params object[] args);//// 摘要://     Formats and writes a log message at the specified log level.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   logLevel://     Entry will be written on this level.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message.////   args://     An object array that contains zero or more objects to format.public static void Log(this ILogger logger, LogLevel logLevel, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a critical log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogCritical(this ILogger logger, string message, params object[] args);//// 摘要://     Formats and writes a critical log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogCritical(this ILogger logger, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a critical log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogCritical(this ILogger logger, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes a critical log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogCritical(this ILogger logger, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a debug log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogDebug(this ILogger logger, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a debug log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogDebug(this ILogger logger, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes a debug log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogDebug(this ILogger logger, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a debug log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogDebug(this ILogger logger, string message, params object[] args);//// 摘要://     Formats and writes an error log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogError(this ILogger logger, string message, params object[] args);//// 摘要://     Formats and writes an error log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogError(this ILogger logger, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes an error log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogError(this ILogger logger, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes an error log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogError(this ILogger logger, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes an informational log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogInformation(this ILogger logger, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes an informational log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogInformation(this ILogger logger, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes an informational log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogInformation(this ILogger logger, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes an informational log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogInformation(this ILogger logger, string message, params object[] args);//// 摘要://     Formats and writes a trace log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogTrace(this ILogger logger, string message, params object[] args);//// 摘要://     Formats and writes a trace log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogTrace(this ILogger logger, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a trace log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogTrace(this ILogger logger, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes a trace log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogTrace(this ILogger logger, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a warning log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogWarning(this ILogger logger, EventId eventId, string message, params object[] args);//// 摘要://     Formats and writes a warning log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   eventId://     The event id associated with the log.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogWarning(this ILogger logger, EventId eventId, Exception exception, string message, params object[] args);//// 摘要://     Formats and writes a warning log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogWarning(this ILogger logger, string message, params object[] args);//// 摘要://     Formats and writes a warning log message.//// 參數://   logger://     The Microsoft.Extensions.Logging.ILogger to write to.////   exception://     The exception to log.////   message://     Format string of the log message in message template format. Example: "User {User}//     logged in from {Address}"////   args://     An object array that contains zero or more objects to format.public static void LogWarning(this ILogger logger, Exception exception, string message, params object[] args);

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