asp.net利用log4net写入日志到SqlServer数据库，Log4net是一个开源的错误日志记录项目，易用性强，源自log4j，品质值得信赖。 下面就我的安装部署log4net到MS sql server的经验与大家分享。
下载log4net的Dll文件并引入到项目中，在你的web主项目（比如MainWeb.csproj）添加对log4net.dll的引用，并在相应的Globall.cs文件中的Application_Start 事件中写入
protected void Application_Start(Object sender, EventArgs e)
{
log4net.Config.XmlConfigurator.Configure( new System.IO.FileInfo( "log4net.config" ));
}
在这个项目对应的Assembly.cs文件中添加一行
[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config" , Watch = true )]
添加logn4net.confgi在主项目根目录下：与web.config同路径，之所以不写入web,config文件， 是因为这样可以单独修改调试部署，也就是非侵入式安装的思想。
<?xml version="1.0"?>
<configuration>
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>
<!--Log4net Begin by Tony 2008.11.20-->
<log4net>
<appender name="ADONetAppender" type="log4net.Appender.ADONetAppender">
<bufferSize value="10" />
<connectionType value="System.Data.SqlClient.SqlConnection, System.Data, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
<connectionString value="DATABASE=DBErrorLogs;SERVER=myserver;UID=user;PWD=pwdpwd;Connect Timeout=15;" />
<commandText value="INSERT INTO ErrorLog ([dtDate],[sThread],[sLevel],[sLogger],[sMessage],[sException]) VALUES (@log_date, @thread, @log_level, @logger, @message, @exception)" />
<parameter>
<parameterName value="@log_date" />
<dbType value="DateTime" />
<layout type="log4net.Layout.RawTimeStampLayout" />
</parameter>
<parameter>
<parameterName value="@thread" />
<dbType value="String" />
<size value="100" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%t" />
</layout>
</parameter>
<parameter>
<parameterName value="@log_level" />
<dbType value="String" />
<size value="200" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%p" />
</layout>
</parameter>
<parameter>
<parameterName value="@logger" />
<dbType value="String" />
<size value="500" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%logger" />
</layout>
</parameter>
<parameter>
<parameterName value="@message" />
<dbType value="String" />
<size value="3000" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%m" />
</layout>
</parameter>
<parameter>
<parameterName value="@exception" />
<dbType value="String" />
<size value="4000" />
<layout type="log4net.Layout.ExceptionLayout" />
</parameter>
</appender>
<!-- setup the root category, add the appenders and set the default level -->
<root>
<level value="WARN"/>
<level value="INFO"/>
<level value="DEBUG"/>
<level value="FINE"/>
<appender-ref ref="ADONetAppender" />
</root>
<!-- specify the level for some specific categories -->
<logger name="iNotes">
<level value="WARN"/>
<level value="INFO"/>
<level value="DEBUG"/>
<level value="FINE"/>
<appender-ref ref="ADONetAppender"/>
</logger>
<logger name="StellaLogger">
<level value="ALL"/>
<appender-ref ref="AdoNetAppender" />
</logger>
</log4net>
<!--Log4net End-->
</configuration>
基本完成了！需要注意的一个参数 bufferSize=10 表示是记录10 条到缓冲区，满10条后再写入SQL server,测试时将其改为1，生产环境建议100
CREATE TABLE [dbo].[ErrorLog](
[nId] [bigint] IDENTITY(1,1) NOT NULL,
[dtDate] [datetime] NOT NULL,
[sThread] [nvarchar](100) NOT NULL,
[sLevel] [nvarchar](200) NOT NULL,
[sLogger] [nvarchar](500) NOT NULL,
[sMessage] [nvarchar](3000) NOT NULL,
[sException] [nvarchar](4000) NULL)
调用代码
public static class TestLog4
{
private static log4net.ILog myLogger = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
public static void OnReceiveMsg()
{
myLogger.Debug("系统已记录错误，请联系管理员！");
}
}