When an unhandled exception is thrown in a Microsoft
ASP.NET-based application that is built on the Microsoft .NET Framework 2.0,
the application unexpectedly quits. When this problem occurs, no exception
information that you must have to understanding the issue is logged in the
Application log.
However, an event message that is similar to the
following may be logged in the System log:
Event Type:
Warning Event Source: W3SVC Event Category: None Event ID: 1009
Date: 9/28/2005 Time: 3:18:11 PM User: N/A Computer:
IIS-SERVER Description: A process serving application pool
‘DefaultAppPool’ terminated unexpectedly. The process id was ‘2548’. The
process exit code was ‘0xe0434f4d’.
Additionally, an event message
that is similar to the following may be logged in the Application log:
This problem occurs because the default policy for unhandled
exceptions has changed in the .NET Framework 2.0. By default, the policy for
unhandled exceptions is to end the worker process.
In the Microsoft
.NET Framework 1.1 and in the Microsoft .NET Framework 1.0, unhandled
exceptions on managed threads were ignored. Unless you attached a debugger to
catch the exception, you would not realize that anything was
wrong.
ASP.NET uses the default policy for unhandled exceptions in the
.NET Framework 2.0. When an unhandled exception is thrown, the ASP.NET-based
application unexpectedly quits.
This behavior does not apply to
exceptions that occur in the context of a request. These kinds of exceptions
are still handled and wrapped by an HttpException object. Exceptions that occur in the context of a request do not
cause the worker process to end. However, unhandled exceptions outside the
context of a request, such as exceptions on a timer thread or in a callback
function, cause the worker process to end.
Modify the source code for the IHttpModule object so that it will log exception information to the
Application log. The information that is logged will include the following:
•
The virtual directory path in which the exception
occurred
•
The exception name
•
The message
•
The stack trace
To modify the IHttpModule object, follow these steps.
Note This code will log a message that has the Event Type of Error and the Event Source of ASP.NET 2.0.50727.0 in the Application log. To test the module, request an ASP.NET
page that uses the ThreadPool.QueueUserWorkItem method to call a method that throws an unhandled exception.
1.
Put the following code in a file that is named
UnhandledExceptionModule.cs.
using System;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Web;
namespace WebMonitor {
public class UnhandledExceptionModule: IHttpModule {
static int _unhandledExceptionCount = 0;
static string _sourceName = null;
static object _initLock = new object();
static bool _initialized = false;
public void Init(HttpApplication app) {
// Do this one time for each AppDomain.
if (!_initialized) {
lock (_initLock) {
if (!_initialized) {
string webenginePath = Path.Combine(RuntimeEnvironment.GetRuntimeDirectory(), "webengine.dll");
if (!File.Exists(webenginePath)) {
throw new Exception(String.Format(CultureInfo.InvariantCulture,
"Failed to locate webengine.dll at '{0}'. This module requires .NET Framework 2.0.",
webenginePath));
}
FileVersionInfo ver = FileVersionInfo.GetVersionInfo(webenginePath);
_sourceName = string.Format(CultureInfo.InvariantCulture, "ASP.NET {0}.{1}.{2}.0",
ver.FileMajorPart, ver.FileMinorPart, ver.FileBuildPart);
if (!EventLog.SourceExists(_sourceName)) {
throw new Exception(String.Format(CultureInfo.InvariantCulture,
"There is no EventLog source named '{0}'. This module requires .NET Framework 2.0.",
_sourceName));
}
AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(OnUnhandledException);
_initialized = true;
}
}
}
}
public void Dispose() {
}
void OnUnhandledException(object o, UnhandledExceptionEventArgs e) {
// Let this occur one time for each AppDomain.
if (Interlocked.Exchange(ref _unhandledExceptionCount, 1) != 0)
return;
StringBuilder message = new StringBuilder("\r\n\r\nUnhandledException logged by UnhandledExceptionModule.dll:\r\n\r\nappId=");
string appId = (string) AppDomain.CurrentDomain.GetData(".appId");
if (appId != null) {
message.Append(appId);
}
Exception currentException = null;
for (currentException = (Exception)e.ExceptionObject; currentException != null; currentException = currentException.InnerException) {
message.AppendFormat("\r\n\r\ntype={0}\r\n\r\nmessage={1}\r\n\r\nstack=\r\n{2}\r\n\r\n",
currentException.GetType().FullName,
currentException.Message,
currentException.StackTrace);
}
EventLog Log = new EventLog();
Log.Source = _sourceName;
Log.WriteEntry(message.ToString(), EventLogEntryType.Error);
}
}
}
2.
Save the UnhandledExceptionModule.cs file to the following
folder:
C:\Program Files\Microsoft Visual Studio 8\VC
3.
Open the Microsoft Visual Studio 2005 Command
Prompt.
4.
Type sn.exe -k key.snk, and then
press ENTER.
5.
Type csc /t:library /r:system.web.dll,system.dll
/keyfile:key.snk UnhandledExceptionModule.cs, and then press
ENTER.
6.
Type gacutil.exe /if
UnhandledExceptionModule.dll, and then press ENTER.
7.
Type ngen install
UnhandledExceptionModule.dll, and then press ENTER.
8.
Type gacutil /l
UnhandledExceptionModule, and then press ENTER to display the
strong name for the UnhandledExceptionModule file.
9.
9. Add the following code to the Web.config file of your
ASP.NET-based application.
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