Based on OP detailed needs explained in comments, a more appropriate solution exists.
The OP states he wishes to add custom data in its logs with log4net, data related to requests.
Rather than wrapping each log4net call into a custom centralized log call which handles retrieving request related data (on each log call), log4net features context dictionaries for setting up custom additional data to log. Using those dictionnaries allows to position your request log data for current request at BeginRequest event, then to dismiss it at EndRequest event. Any log in between will benefit from these custom data.
And things that do not happen in a request context will not try to log request related data, eliminating the need to test for request availability. This solution matches the principle Arman McHitaryan was suggesting in his answer.
For this solution to work, you will also need some additional configuration on your log4net appenders in order for them to log your custom data.
This solution can be easily implemented as a custom log enhancement module. Here is some sample code for it:
using System;
using System.Web;
using log4net;
using log4net.Core;
namespace YourNameSpace
{
public class LogHttpModule : IHttpModule
{
public void Dispose()
{
// nothing to free
}
private const string _ipKey = "IP";
private const string _urlKey = "URL";
private const string _refererKey = "Referer";
private const string _userAgentKey = "UserAgent";
private const string _userNameKey = "userName";
public void Init(HttpApplication context)
{
context.BeginRequest += WebAppli_BeginRequest;
context.PostAuthenticateRequest += WebAppli_PostAuthenticateRequest;
// All custom properties must be initialized, otherwise log4net will not get
// them from HttpContext.
InitValueProviders(_ipKey, _urlKey, _refererKey, _userAgentKey,
_userNameKey);
}
private void InitValueProviders(params string[] valueKeys)
{
if (valueKeys == null)
return;
foreach(var key in valueKeys)
{
GlobalContext.Properties[key] = new HttpContextValueProvider(key);
}
}
private void WebAppli_BeginRequest(object sender, EventArgs e)
{
var currContext = HttpContext.Current;
currContext.Items[_ipKey] = currContext.Request.UserHostAddress;
currContext.Items[_urlKey] = currContext.Request.Url.AbsoluteUri;
currContext.Items[_refererKey] = currContext.Request.UrlReferrer != null ?
currContext.Request.UrlReferrer.AbsoluteUri : null;
currContext.Items[_userAgentKey] = currContext.Request.UserAgent;
}
private void WebAppli_PostAuthenticateRequest(object sender, EventArgs e)
{
var currContext = HttpContext.Current;
// log4net doc states that %identity is "extremely slow":
// http://logging.apache.org/log4net/release/sdk/log4net.Layout.PatternLayout.html
// So here is some custom retrieval logic for it, so bad, especialy since I
// tend to think this is a missed copy/paste in that documentation.
// Indeed, we can find by inspection in default properties fetch by log4net a
// log4net:Identity property with the data, but it looks undocumented...
currContext.Items[_userNameKey] = currContext.User.Identity.Name;
}
}
// General idea coming from
// http://piers7.blogspot.fr/2005/12/log4net-context-problems-with-aspnet.html
// We can not use log4net ThreadContext or LogicalThreadContext with asp.net, since
// asp.net may switch thread while serving a request, and reset the call context
// in the process.
public class HttpContextValueProvider : IFixingRequired
{
private string _contextKey;
public HttpContextValueProvider(string contextKey)
{
_contextKey = contextKey;
}
public override string ToString()
{
var currContext = HttpContext.Current;
if (currContext == null)
return null;
var value = currContext.Items[_contextKey];
if (value == null)
return null;
return value.ToString();
}
object IFixingRequired.GetFixedObject()
{
return ToString();
}
}
}
Add it to your site, IIS 7+ configuration sample:
<system.webServer>
<!-- other stuff removed ... -->
<modules>
<!-- other stuff removed ... -->
<add name="LogEnhancer" type="YourNameSpace.LogHttpModule, YourAssemblyName" preCondition="managedHandler" />
<!-- other stuff removed ... -->
</modules>
<!-- other stuff removed ... -->
</system.webServer>
And set up appenders to log those additional properties, sample config:
<log4net>
<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
<!-- other stuff removed ... -->
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %-5level %logger - %message - %property%newline%exception" />
</layout>
</appender>
<appender name="SqlAppender" type="log4net.Appender.AdoNetAppender">
<!-- other stuff removed ... -->
<commandText value="INSERT INTO YourLogTable ([Date],[Thread],[Level],[Logger],[UserName],[Message],[Exception],[Ip],[Url],[Referer],[UserAgent]) VALUES (@log_date, @thread, @log_level, @logger, @userName, @message, @exception, @Ip, @Url, @Referer, @UserAgent)" />
<!-- other parameters removed ... -->
<parameter>
<parameterName value="@userName" />
<dbType value="String" />
<size value="255" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%property{userName}" />
</layout>
</parameter>
<parameter>
<parameterName value="@Ip"/>
<dbType value="String" />
<size value="255" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%property{Ip}" />
</layout>
</parameter>
<parameter>
<parameterName value="@Url"/>
<dbType value="String" />
<size value="255" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%property{Url}" />
</layout>
</parameter>
<parameter>
<parameterName value="@Referer"/>
<dbType value="String" />
<size value="255" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%property{Referer}" />
</layout>
</parameter>
<parameter>
<parameterName value="@UserAgent"/>
<dbType value="String" />
<size value="255" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%property{UserAgent}" />
</layout>
</parameter>
</appender>
<!-- other stuff removed ... -->
</log4net>
