How do I Handle Errors and Send an Error Notification from ASP.NET Applications?

1. First you need to turn on custom errors in your Web.Config file and provide the page that will be shown when a status code 500 error occurs:
   
   

   <customErrors mode="On">
     <error statusCode="500" redirect="/InternalError.htm"/>
   </customErrors>

2. Next, modify the Global class to wire into the Application_Error event. To make this work, add the following code to the Application_Error method in the Code Behind of your Global.asax page:
   
   

   protected void Application_Error(Object sender, EventArgs e)
   {

     StringBuilder ErrorMessage = new StringBuilder();
     Exception myError = null;
   
     myError = Server.GetLastError();
   
     if (myError != null)
     {
       while (myError.InnerException != null)
       {
         // Assign the next InnerException
         // to drill down to the lowest level exception
         myError = myError.InnerException;
       }
   
       ErrorMessage.Append("Message\r\n" + 
         myError.Message.ToString() + "\r\n\r\n");
       ErrorMessage.Append("Source\r\n" + 
         myError.Source + "\r\n\r\n");
       ErrorMessage.Append("Target site\r\n" + 
         myError.TargetSite.ToString() + "\r\n\r\n");
       ErrorMessage.Append("Stack trace\r\n" + 
         myError.StackTrace + "\r\n\r\n");
       ErrorMessage.Append("ToString()\r\n" + 
         myError.ToString() + "\r\n\r\n");
   
       MailMessage objMail = new MailMessage();
       objMail.To = "You@YourISP.com";
       objMail.From = "YourSite@YourISP.Com";
       objMail.Subject = "Error 500 in: " + Request.Url.ToString() 
         + " at " + DateTime.Now.ToString();
       objMail.BodyFormat = MailFormat.Text;
       objMail.Body = ErrorMessage.ToString();
       SmtpMail.SmtpServer = "YourMailServer";
       SmtpMail.Send(objMail);
     }

   }

while (myError.InnerException != null)
{
  // Assign the next InnerException
  // to drill down to the lowest level exception
  myError = myError.InnerException;
}

Instead of looping through the exceptions, you can also call GetBaseException() to get at the inner most exception directly:

myError = Server.GetLastError().GetBaseException();
	
myErrorMessage += "Message\r\n" +
	myError.Message.ToString() + "\r\n\r\n";
myErrorMessage += "Source\r\n" +
	myError.Source + "\r\n\r\n";
myErrorMessage += "Target site\r\n" +
	myError.TargetSite.ToString() + "\r\n\r\n";
myErrorMessage += "Stack trace\r\n" +
	myError.StackTrace + "\r\n\r\n";
myErrorMessage += "ToString()\r\n\r\n" +
	myError.ToString();

For all this code to work, you'll need to import the following two namespaces in your Global class:

using System.Text;
using System.Web.Mail;