Global Exception Handling in ASP.NET

using System;
using System.Web;
using System.Web.Mail;
using System.Configuration;
using System.Diagnostics;
using System.Text;
using System.IO;

namespace XC.Web
{
	public class ErrorHandler
	{
		public const int UseEventLog = 1;
		public const int UseFile = 2;
		public const int UseEmail = 4;
		
		int m_notifyMode = 0;
		
		EmailNotificationSettings m_emailSettings = new EmailNotificationSettings();
		FileNotificationSettings  m_fileSettings  = new FileNotificationSettings();
		EventLogSettings          m_logSettings   = new EventLogSettings();


		public ErrorHandler()
		{
			if (ConfigurationSettings.AppSettings["errorNotifier_NotifyMode"] == null)
			{
				NotifyMode = UseFile;
			}
			else
			{
				NotifyMode = int.Parse(ConfigurationSettings.AppSettings["errorNotifier_NotifyMode"]);
			}
		}

		public int NotifyMode
		{
			get { return m_notifyMode;  }
			set { m_notifyMode = value; }
		}
		
		public EmailNotificationSettings EmailSettings
		{
			get { return m_emailSettings;  }
			set { m_emailSettings = value; }
		}

		public FileNotificationSettings FileSettings
		{
			get { return m_fileSettings;  }
			set { m_fileSettings = value; }
		}

		public EventLogSettings LogSettings
		{
			get { return m_logSettings;  }
			set { m_logSettings = value; }
		}

		public void HandleException()
		{
			Exception e = HttpContext.Current.Server.GetLastError();

			if (e == null)
				return;

			e = e.GetBaseException();
			
			if (e != null)
				HandleException(e);
		}

		public void HandleException(Exception e)
		{
			string sExceptionDescription = FormatExceptionDescription(e);

			if ((NotifyMode & UseFile) == UseFile)
			{
				WriteToFile(sExceptionDescription);
			}

			if ((NotifyMode & UseEmail) == UseEmail)
			{
				SendEmail(sExceptionDescription);
			}			

			if ((NotifyMode & UseEventLog) == UseEventLog)
			{
				LogEvent(sExceptionDescription);
			}
		}

		protected virtual string FormatExceptionDescription(Exception e)
		{
			StringBuilder sb = new StringBuilder();
			HttpContext context = HttpContext.Current;

			sb.Append("Time of Error: " + DateTime.Now.ToString("g") + Environment.NewLine);
			sb.Append("URL: " + context.Request.Url + Environment.NewLine);
			sb.Append("Form: " + context.Request.Form.ToString() + Environment.NewLine);
			sb.Append("QueryString: " + context.Request.QueryString.ToString() + Environment.NewLine);			
			sb.Append("Server Name: " + context.Request.ServerVariables["SERVER_NAME"] + Environment.NewLine);
			sb.Append("User Agent: " + context.Request.UserAgent + Environment.NewLine);
			sb.Append("User IP: " + context.Request.UserHostAddress + Environment.NewLine);
			sb.Append("User Host Name: " + context.Request.UserHostName + Environment.NewLine);
			sb.Append("User is Authenticated: " + context.User.Identity.IsAuthenticated.ToString() + Environment.NewLine);
			sb.Append("User Name: " + context.User.Identity.Name + Environment.NewLine);
			

			while (e != null)
			{				
				sb.Append("Message: " + e.Message + Environment.NewLine);
				sb.Append("Source: " + e.Source+ Environment.NewLine);
				sb.Append("TargetSite: " + e.TargetSite + Environment.NewLine);
				sb.Append("StackTrace: " + e.StackTrace + Environment.NewLine);
				sb.Append(Environment.NewLine + Environment.NewLine);

				e = e.InnerException;
			}
			
			sb.Append("\n\n");
			return sb.ToString();
		}

		void WriteToFile(string sText)
		{
			string sPath = HttpContext.Current.Server.MapPath(FileSettings.Filename);
			try
			{
				FileStream fs = new FileStream(sPath, FileMode.Append, FileAccess.Write);
				StreamWriter writer = new StreamWriter(fs);
				writer.Write(sText);
				writer.Close();
				fs.Close();
			}
			catch (Exception )
			{
			}
		}

		void SendEmail(string sBody)
		{
			MailMessage msg = new MailMessage();

			msg.BodyFormat = MailFormat.Text;
			msg.To         = EmailSettings.To;
			msg.From       = EmailSettings.From;
			msg.Subject    = EmailSettings.Subject;
			msg.Body       = sBody;

			try
			{
				if (EmailSettings.SmtpServer != null)
					SmtpMail.SmtpServer = EmailSettings.SmtpServer;

				SmtpMail.Send(msg);
			}
			catch (Exception )
			{
			}
		}

		void LogEvent(string sText)
		{	
			try
			{
				if (!EventLog.SourceExists(LogSettings.EventSource))
				{
					EventLog.CreateEventSource(LogSettings.EventSource, "Application");
				}

				EventLog log = new EventLog();
				log.Source = LogSettings.EventSource;
				log.WriteEntry(sText, EventLogEntryType.Error);
			}
			catch (Exception )
			{
			}

		}

		public void ClearLoggedFileErrors()
		{
			try
			{
				File.Delete(HttpContext.Current.Server.MapPath(FileSettings.Filename));
			}
			catch (Exception )
			{
			}
		}


	}
}