How to use UnhandledException to handle all unhandled exceptions?

[OMID SOFT]

An application raises the UnhandledException event when it encounters an unhandled exception.

For instance, you can use this event to ask user send you a report by email.

Private Sub UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs)

If MessageBox.Show("Unhandled exception has occurred in My Application." + vbNewLine + "We ask you to report this error to My Company." + vbNewLine + "Would you like to send a report via email?", My.Application.Info.AssemblyName, MessageBoxButtons.YesNo, MessageBoxIcon.Error) = DialogResult.Yes Then

Dim MyString As String = Nothing

MyString = ("x-receiver: <user@company.com>" + vbNewLine)

MyString = MyString + ("To: ""user@company.com"" <user@company.com>" + vbNewLine)

MyString = MyString + ("Subject: Bug Report - My Product " + My.Application.Info.Version.Major.ToString + "." + My.Application.Info.Version.Minor.ToString + vbNewLine)

MyString = MyString + ("Date: " + Now.DayOfWeek.ToString.Substring(0, 3) + ", " + Now.ToString("dd") + " " + Now.ToString("MMMM").Substring(0, 3) + " " + Now.ToString("yyyy") + " " + Now.ToString("HH:mm:ss") + " " + TimeZone.CurrentTimeZone.GetUtcOffset(Now).ToString.Replace(":", "").Substring(0, 5) + vbNewLine)

MyString = MyString + ("X-Priority: 3" + vbNewLine)

MyString = MyString + ("MIME-Version: 1.0" + vbNewLine)

MyString = MyString + ("Content-type: text/plain; charset=Windows-1252" + vbNewLine)

MyString = MyString + ("Content-Transfer-Encoding: quoted-printable" + vbNewLine + vbNewLine)

MyString = MyString + (e.Exception.ToString + vbNewLine)

Dim TempPath As String = System.IO.Path.GetTempPath + "Report_" + Now.ToString("MM-dd-yyyy") + "_" + Now.ToString("HH-mm-ss") + ".eml"

If My.Computer.FileSystem.FileExists(TempPath) Then

System.IO.File.SetAttributes(TempPath, FileAttributes.Normal)

My.Computer.FileSystem.DeleteFile(TempPath)

End If

My.Computer.FileSystem.WriteAllText(TempPath, MyString, False)

System.Diagnostics.Process.Start(TempPath)

End If

End Sub

Why you should NOT use this event?

Although this is a useful event to control, debug and report the errors, but Microsoft does not recommend to use it.

According to Certified For Windows Vista guidelines:

Verify that the application only handles exceptions that are known and expected. (Test Case number 32.)

Expected Behaviour:

1. All of the application’s executables above; when injected Access Violation (AV) resulted in the application crashing and must display the WER (Windows Error Reporting) dialog message in order to pass this test case. This means that the application AV failure properly allowed Windows Error Reporting to report this crash.

2. There must be both an Error message with “Source” listed as Application Error and an Information message with “Source” listed as Windows Error Reporting for each executable above in order to pass this test case.

STEPS:

1. Browse application install paths for all executables which contain only the .exe extension.

2. For each of the application’s executables above:

a. Launch the application’s executable.

b. Open command window.

c. Change directories to the directory that contains ThreadHijacker.

d. From the command window inject an AV crash using ThreadHijacker in the following manner:

i. Type “threadhijacker.exe /ui /crash:av /process:<process_name>”

e. Open Event Viewer by typing eventvwr from the command line or from the Administrator Tools.

i. Expand Windows Logs

ii. Click on Application

iii. There must be an Application Error (Error) and Window Error Reporting (Information) message for the executable.

 

[Diesel]

Microsoft wants to be able to handle the exception, to make sure that it wasn't their fault that it was caused in the first place, ie. invalid data in memory.

You can handle the exception, just make sure you rethrow the error. If you don't want the Windows Exception dialog to show up, exit the program. Just make sure the application exits after handling the exception, otherwise you don't know what state your application is in and it could cause damage.