通过XML配置NLog，但以编程方式配置

What? Did you know that you can specify the NLog XML directly to NLog from your app, as opposed to having NLog read it from the config file? Well, you can. Let's say that you have a distributed app and you want to use the same configuration everywhere. You could keep a config file in each location and maintain it separately, you could maintain one in a central location and push it out to the satellite locations, or you could probably do a lot of other things. Or, you could store your XML in a database, get it at app startup, and configure NLog directly with that XML (maybe checking back periodically to see if it had changed).

  string xml = @"<nlog>
                   <targets>
                     <target name='console' type='Console' layout='${message}' />
                   </targets>

                   <rules>
                     <logger name='*' minlevel='Error' writeTo='console' />
                   </rules>
                 </nlog>";

  StringReader sr = new StringReader(xml);
  XmlReader xr = XmlReader.Create(sr);
  XmlLoggingConfiguration config = new XmlLoggingConfiguration(xr, null);
  LogManager.Configuration = config;
  //NLog is now configured just as if the XML above had been in NLog.config or app.config

  logger.Trace("Hello - Trace"); //Won't log
  logger.Debug("Hello - Debug"); //Won't log
  logger.Info("Hello - Info");   //Won't log
  logger.Warn("Hello - Warn");   //Won't log
  logger.Error("Hello - Error"); //Will log
  logger.Fatal("Hello - Fatal"); //Will log

  //Now let's change the config (the root logging level) ...
  string xml2 = @"<nlog>
                  <targets>
                     <target name='console' type='Console' layout='${message}' />
                   </targets>

                   <rules>
                     <logger name='*' minlevel='Trace' writeTo='console' />
                   </rules>
                 </nlog>";

  StringReader sr2 = new StringReader(xml2);
  XmlReader xr2 = XmlReader.Create(sr2);
  XmlLoggingConfiguration config2 = new XmlLoggingConfiguration(xr2, null);
  LogManager.Configuration = config2;

  logger.Trace("Hello - Trace"); //Will log
  logger.Debug("Hello - Debug"); //Will log
  logger.Info("Hello - Info");   //Will log
  logger.Warn("Hello - Warn");   //Will log
  logger.Error("Hello - Error"); //Will log
  logger.Fatal("Hello - Fatal"); //Will log

我不确定这有多健壮，但是这个例子为那些想尝试这样配置的人提供了一个有用的起点。

显然，你现在可以在Windows上使用NLog和Growl了。

<?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">

    <extensions>
        <add assembly="NLog.Targets.GrowlNotify" />
    </extensions>

    <targets>
        <target name="growl" type="GrowlNotify" password="" host="" port="" />
    </targets>

    <rules>
        <logger name="*" minLevel="Trace" appendTo="growl"/>
    </rules>

</nlog>

根据是否有错误记录不同的级别

此示例允许您在代码中出现错误时获取更多信息。基本上，它缓冲消息，只输出那些在一定的日志级别(例如警告)，除非满足一定的条件(例如，有一个错误，所以日志级别是>=错误)，然后它将输出更多的信息(例如，所有来自日志级别>= Trace的消息)。因为消息是缓冲的，这让您可以收集关于在Error或ErrorException被记录之前发生了什么的跟踪信息——非常有用!

I adapted this one from an example in the source code. I was thrown at first because I left out the AspNetBufferingWrapper (since mine isn't an ASP app) - it turns out that the PostFilteringWrapper requires some buffered target. Note that the target-ref element used in the above-linked example cannot be used in NLog 1.0 (I am using 1.0 Refresh for a .NET 4.0 app); it is necessary to put your target inside the wrapper block. Also note that the logic syntax (i.e. greater-than or less-than symbols, < and >) has to use the symbols, not the XML escapes for those symbols (i.e. &gt; and &lt;) or else NLog will error.

app.config:

<?xml version="1.0"?>
<configuration>
    <configSections>
        <section name="nlog" type="NLog.Config.ConfigSectionHandler, NLog"/>
    </configSections>

    <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          throwExceptions="true" internalLogToConsole="true" internalLogLevel="Warn" internalLogFile="nlog.log">
        <variable name="appTitle" value="My app"/>
        <variable name="csvPath" value="${specialfolder:folder=Desktop:file=${appTitle} log.csv}"/>

        <targets async="true">
            <!--The following will keep the default number of log messages in a buffer and write out certain levels if there is an error and other levels if there is not. Messages that appeared before the error (in code) will be included, since they are buffered.-->
            <wrapper-target xsi:type="BufferingWrapper" name="smartLog">
                <wrapper-target xsi:type="PostFilteringWrapper">
                    <!--<target-ref name="fileAsCsv"/>-->
                    <target xsi:type="File" fileName="${csvPath}"
                    archiveAboveSize="4194304" concurrentWrites="false" maxArchiveFiles="1" archiveNumbering="Sequence"
                    >
                        <layout xsi:type="CsvLayout" delimiter="Tab" withHeader="false">
                            <column name="time" layout="${longdate}" />
                            <column name="level" layout="${level:upperCase=true}"/>
                            <column name="message" layout="${message}" />
                            <column name="callsite" layout="${callsite:includeSourcePath=true}" />
                            <column name="stacktrace" layout="${stacktrace:topFrames=10}" />
                            <column name="exception" layout="${exception:format=ToString}"/>
                            <!--<column name="logger" layout="${logger}"/>-->
                        </layout>
                    </target>

                     <!--during normal execution only log certain messages--> 
                    <defaultFilter>level >= LogLevel.Warn</defaultFilter>

                     <!--if there is at least one error, log everything from trace level--> 
                    <when exists="level >= LogLevel.Error" filter="level >= LogLevel.Trace" />
                </wrapper-target>
            </wrapper-target>

        </targets>

        <rules>
            <logger name="*" minlevel="Trace" writeTo="smartLog"/>
        </rules>
    </nlog>
</configuration>

区别对待异常

当出现异常时，我们通常希望获得更多信息。下面的配置有两个目标，一个文件和控制台，它们根据是否有任何异常信息进行筛选。(编辑:Jarek已经在vNext中发布了一种新方法。)

关键是要有一个包装器目标xsi:type="FilteringWrapper" condition="length('${exception}')>0"

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.mono2.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      autoReload="true"
      internalLogLevel="Warn"
      internalLogFile="nlog log.log"
      >
    <variable name="VerboseLayout" 
              value="${longdate} ${level:upperCase=true} ${message}  
                    (${callsite:includSourcePath=true})"            />
    <variable name="ExceptionVerboseLayout"  
              value="${VerboseLayout} (${stacktrace:topFrames=10})  
                     ${exception:format=ToString}"                  />

    <targets async="true">
        <target name="file" xsi:type="File" fileName="log.log"
                layout="${VerboseLayout}">
        </target>

        <target name="fileAsException"  
                xsi:type="FilteringWrapper" 
                condition="length('${exception}')>0">
            <target xsi:type="File"  
                    fileName="log.log"  
                    layout="${ExceptionVerboseLayout}" />
        </target>

        <target xsi:type="ColoredConsole"
                name="console"
                layout="${NormalLayout}"/>

        <target xsi:type="FilteringWrapper"  
                condition="length('${exception}')>0"  
                name="consoleException">
            <target xsi:type="ColoredConsole" 
                    layout="${ExceptionVerboseLayout}" />
        </target>
    </targets>

    <rules>
        <logger name="*" minlevel="Trace" writeTo="console,consoleException" />
        <logger name="*" minlevel="Warn" writeTo="file,fileAsException" />
    </rules>

</nlog>

登录Twitter

Based on this post about a log4net Twitter Appender, I thought I would try my hand at writing a NLog Twitter Target (using NLog 1.0 refresh, not 2.0). Alas, so far I have not been able to get a Tweet to actually post successfully. I don't know if it is something wrong in my code, Twitter, our company's internet connection/firewall, or what. I am posting the code here in case someone is interested in trying it out. Note that there are three different "Post" methods. The first one that I tried is PostMessageToTwitter. PostMessageToTwitter is essentially the same as PostLoggingEvent in the orignal post. If I use that I get a 401 exception. PostMessageBasic gets the same exception. PostMessage runs with no errors, but the message still does not make it up to Twitter. PostMessage and PostMessageBasic are based on examples that I found here on SO.

仅供参考——我刚刚发现了@Jason Diller对这篇文章的一个回答的评论，他说twitter将在下个月关闭基本的身份验证。这是在2010年5月，现在是2010年12月，所以我想这可能就是为什么它不起作用的原因。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Web;
using System.IO;

using NLog;
using NLog.Targets;
using NLog.Config;

namespace NLogExtensions
{
  [Target("TwitterTarget")]
  public class TwitterTarget : TargetWithLayout
  {
    private const string REQUEST_CONTENT_TYPE = "application/x-www-form-urlencoded";  

    private const string REQUEST_METHOD = "POST";  

    // The source attribute has been removed from the Twitter API,  
    // unless you're using OAuth.  
    // Even if you are using OAuth, there's still an approval process.  
    // Not worth it; "API" will work for now!  
    // private const string TWITTER_SOURCE_NAME = "Log4Net";  
    private const string TWITTER_UPDATE_URL_FORMAT = "http://twitter.com/statuses/update.xml?status={0}";  

    [RequiredParameter]
    public string TwitterUserName { get; set; }

    [RequiredParameter]
    public string TwitterPassword { get; set; }

    protected override void Write(LogEventInfo logEvent)
    {
      if (string.IsNullOrWhiteSpace(TwitterUserName) || string.IsNullOrWhiteSpace(TwitterPassword)) return;

      string msg = this.CompiledLayout.GetFormattedMessage(logEvent);

      if (string.IsNullOrWhiteSpace(msg)) return;

      try
      {
        //PostMessageToTwitter(msg);
        PostMessageBasic(msg);
      }
      catch (Exception ex)
      {
        //Should probably do something here ...
      }
    }

    private void PostMessageBasic(string msg)
    {
      // Create a webclient with the twitter account credentials, which will be used to set the HTTP header for basic authentication 
      WebClient client = new WebClient { Credentials = new NetworkCredential { UserName = TwitterUserName, Password = TwitterPassword } };

      // Don't wait to receive a 100 Continue HTTP response from the server before sending out the message body 
      ServicePointManager.Expect100Continue = false;

      // Construct the message body 
      byte[] messageBody = Encoding.ASCII.GetBytes("status=" + msg);

      // Send the HTTP headers and message body (a.k.a. Post the data) 
      client.UploadData(@"http://twitter.com/statuses/update.xml", messageBody);
    }

    private void PostMessage(string msg)
    {
      string user = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(TwitterUserName + ":" + TwitterPassword));
      byte [] bytes = System.Text.Encoding.UTF8.GetBytes("status=" + msg.ToTweet());
      HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://twitter.com/statuses/update.xml");
      request.Method = "POST";
      request.ServicePoint.Expect100Continue = false;
      request.Headers.Add("Authorization", "Basic " + user);
      request.ContentType = "application/x-www-form-urlencoded";
      request.ContentLength = bytes.Length;
      Stream reqStream = request.GetRequestStream();
      reqStream.Write(bytes, 0, bytes.Length);
      reqStream.Close();
    }

    private void PostMessageToTwitter(string msg)
    {
      var updateRequest = HttpWebRequest.Create(string.Format(TWITTER_UPDATE_URL_FORMAT,
                                                HttpUtility.UrlEncode(msg.ToTweet()))) as HttpWebRequest;
      updateRequest.ContentLength = 0;
      updateRequest.ContentType = REQUEST_CONTENT_TYPE;
      updateRequest.Credentials = new NetworkCredential(TwitterUserName, TwitterPassword);
      updateRequest.Method = REQUEST_METHOD;

      updateRequest.ServicePoint.Expect100Continue = false;

      var updateResponse = updateRequest.GetResponse() as HttpWebResponse;

      if (updateResponse.StatusCode != HttpStatusCode.OK && updateResponse.StatusCode != HttpStatusCode.Continue)
      {
        throw new Exception(string.Format("An error occurred while invoking the Twitter REST API [Response Code: {0}]", updateResponse.StatusCode));
      }
    }
  }

  public static class Extensions
  {
    public static string ToTweet(this string s)
    {
      if (string.IsNullOrEmpty(s) || s.Length < 140)
      {
        return s;
      }

      return s.Substring(0, 137) + "...";
    }
  }
}

这样配置:

告诉NLog包含目标的程序集:

<extensions>
  <add assembly="NLogExtensions"/>
</extensions>

配置目标:

<targets>
    <target name="twitter" type="TwitterTarget" TwitterUserName="yourtwittername" TwitterPassword="yourtwitterpassword" layout="${longdate} ${logger} ${level} ${message}" />
</targets>

如果有人尝试了这个方法并取得了成功，请将你的发现反馈给我们。

使用条件布局用不同的布局记录每个日志级别的更简单方法

<variable name="VerboseLayout" value="${level:uppercase=true}: ${longdate} | ${logger}    : 
${when:when=level == LogLevel.Trace:inner=MONITOR_TRACE ${message}} 
${when:when=level == LogLevel.Debug:inner=MONITOR_DEBUG ${message}} 
${when:when=level == LogLevel.Info:inner=MONITOR_INFO ${message}} 
${when:when=level == LogLevel.Warn:inner=MONITOR_WARN ${message}} 
${when:when=level == LogLevel.Error:inner=MONITOR_ERROR ${message}} 
${when:when=level == LogLevel.Fatal:inner=MONITOR_CRITICAL ${message}} |     
${exception:format=tostring} | ${newline} ${newline}" />

参见https://github.com/NLog/NLog/wiki/When-Filter查看语法