Use log4net to Log Errors or Visitors

log4net is a free utility that can be used for logging data about errors or visitors. It is available here: http://logging.apache.org/log4net/index.html

Here is an introductory article: http://www.codeproject.com/KB/trace/Log4Net_with_ASP_NET.aspx

I think a useful way to track users is to log users by their IP Address. Once your log4net is installed correctly, the following code in the Page_Load event can be used to write IP Addresses to a file placed in the App_Code folder (where it is not public):

        if (!Page.IsPostBack)
        {
            string nowip;
            nowip = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if (nowip == null)
            {
                nowip = Request.ServerVariables["REMOTE_ADDR"];
            }
            log.Info("Visitor IP: " + nowip);
        }

I'll include the BasePage for a reference to the log variable above (which the System.Web.Page inherits from):

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using log4net;

public class BasePage : System.Web.UI.Page
{
    public static readonly ILog log = LogManager.GetLogger("Logger");
    public BasePage()
    {
        initLog4Net();
        //logAll();
    }
    /// <summary>
    /// initializes Log4Net 
    /// Described at http://www.codeproject.com/KB/trace/Log4Net_with_ASP_NET.aspx
    /// configured in web.config
    ///     level value can be ALL ERROR DEBUG FATAL DEBUG OFF WARN
    /// </summary>
    private void initLog4Net()
    {
        log4net.Config.XmlConfigurator.Configure();
    }
    /// <summary>
    /// test log4net
    /// </summary>
    protected void logAllTest()
    {
        bool isDebugEnabled = log.IsDebugEnabled;
        bool isErrorEnabled = log.IsErrorEnabled;
        bool isFatalEnabled = log.IsFatalEnabled;
        bool isInfoEnabled = log.IsInfoEnabled;
        bool isWarnEnabled = log.IsWarnEnabled;
        log.Debug("Debug msg");
        log.Error("Error msg");
        log.Fatal("Fatal msg");
        log.Info("Info msg");
        log.Warn("Warn msg");
    }
}

References: http://www.aspxcode.net/free-asp-net-sample-source-code-c.aspx?Topics=how%20to%20get%20the%20IP%20Address%20of%20the%20Visitor