In the previous article on the Log4net configuration, I explain how to configure Log4net with the file appender.
In this article I explain how to configure Log4net with the Sql Server appender.
It is very similar, but we see in detail the new configuration.

Download

You can download the latest version of Log4net from this location.

Add reference to your solution

In Visual Studio 2005 select Project -> Add Reference.
In the tab Browse, find and select the dll Log4net.dll in your local folder.

Modify web.config

Into web.config file add this code into the section Configuration->Configsections:

<configSections>
    <section name="log4net"
      type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" /> 
</configSections>

<log4net>
  <appender name="ADONetAppender" type="log4net.Appender.ADONetAppender">
    <bufferSize value="100" />
    <connectionType value="System.Data.SqlClient.SqlConnection, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
    <connectionString value="server=localhost; uid=; pwd=; database=" />
    <commandText value="INSERT INTO Log ([Date],[Thread],[Level],[Logger],[Message],[Exception]) 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="32" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%t" />
      </layout>
    </parameter>
    <parameter>
      <parameterName value="@log_level" />
      <dbType value="String" />
      <size value="512" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%p" />
      </layout>
    </parameter>
    <parameter>
      <parameterName value="@logger" />
      <dbType value="String" />
      <size value="512" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%c" />
      </layout>
    </parameter>
    <parameter>
      <parameterName value="@message" />
      <dbType value="String" />
      <size value="4000" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%m" />
      </layout>
    </parameter>
    <parameter>
      <parameterName value="@exception" />
      <dbType value="String" />
      <size value="2000" />
      <layout type="log4net.Layout.ExceptionLayout" />
    </parameter>
  </appender>
  <root>
    <level value="DEBUG" />
    <appender-ref ref="ADONetAppender" />
  </root>
</log4net>

Change the connectionstring parameters to connect to your database.

Create the table

In your database, create the table to use Log4net. 

CREATE TABLE [dbo].[Log](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Date] [datetime] NULL,
    [Thread] [varchar](255) NULL,
    [Level] [varchar](50) NULL,
    [Logger] [varchar](255) NULL,
    [Message] [varchar](4000) NULL,
    [Exception] [varchar](2000) NULL
) ON [PRIMARY]

Edit the Global.asax file

In the event "Application_Start" of the file Global.asax add this line:

log4net.Config.XmlConfigurator.Configure();

Begin to log

In every page you want to log something, add the static variable like below:
private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

This class has 5 levels of severity to log the operations:

log.Debug("log something at this level")
log.Info("log something at this level")
log.Warn("log something at this level");
log.Error("log something at this level");
log.Fatal("log something at this level");

You find the official documentation at this link.

If you want to log on the file system, read the previous article on Log4net.