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:
Event Type: Error
Event Source: .NET Runtime 2.0
Error Reporting
Event Category: None
Event ID: 5000
Date:
9/28/2005
Time: 3:18:02 PM
User: N/A
Computer: IIS-SERVER
Description:
EventType clr20r3, P1 w3wp.exe, P2 6.0.3790.1830, P3
42435be1, P4 app_web_7437ep-9, P5 0.0.0.0, P6 433b1670, P7 9, P8 a, P9
system.exception, P10 NIL.
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.
To resolve this problem, use one of the following methods.
Method 1
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.
- 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);
}
}
} - Save the UnhandledExceptionModule.cs file to the following
folder:
C:\Program Files\Microsoft Visual Studio 8\VC
- Open the Microsoft Visual Studio 2005 Command
Prompt.
- Type sn.exe -k key.snk, and then
press ENTER.
- Type csc /t:library /r:system.web.dll,system.dll
/keyfile:key.snk UnhandledExceptionModule.cs, and then press
ENTER.
- Type gacutil.exe /if
UnhandledExceptionModule.dll, and then press ENTER.
- Type ngen install
UnhandledExceptionModule.dll, and then press ENTER.
- Type gacutil /l
UnhandledExceptionModule, and then press ENTER to display the
strong name for the UnhandledExceptionModule file.
- 9. Add the following code to the Web.config file of your
ASP.NET-based application.
<add name="UnhandledExceptionModule"
type="WebMonitor.UnhandledExceptionModule, <strong name>" />
Method 2
Change the unhandled exception policy back to the default behavior
that occurs in the .NET Framework 1.1 and in the .NET Framework 1.0.
Note We do not recommend that you change the default behavior. If you
ignore exceptions, the application may leak resources and abandon
locks.
To enable this default behavior, add the following code to the
Aspnet.config file that is located in the following folder:
%WINDIR%\Microsoft.NET\Framework\v2.0.50727
<configuration>
<runtime>
<legacyUnhandledExceptionPolicy enabled="true" />
</runtime>
</configuration> This
behavior is by design.
For more information about changes in the .NET Framework
2.0, visit the following Microsoft Developer Network (MSDN) Web site: