AppDomain.UnhandledException Part 2

Mon, December 20, 2004, 04:01 PM under MobileAndEmbedded
Below find the VB code for global exception handling in NETCF, as described here. First though, a sort paragraph that you may skip if you desire.

It is worth noting some behaviours of surrounding Application.Run with try..catch (which we already established is not needed). On its own, it cannot catch exceptions thrown from a thread, but it can catch ones thrown on the GUI. It can also catch them when thrown in a Control.Invoke, but only after the built-in CF error dialog appears. If you use try..catch in combination with AD.UnhandledException, it gets more interesting. The try..catch handler is always hit straight after the AppDomain handler with a ThreadAbortException (and a different StackTrace); in those cases, your handling code better run fast, as the process is on its way out and even a MessageBox will not stay up for long. The exception (no pun intended) to the last comment and the order the two handlers are run, is when the exception is thrown on the GUI thread. So, once again, AppDomain.UnhandledException is all you need.

Without further ado here is the VB version:

Public NotInheritable Class EntryPoint
Private Sub New()
End Sub

<MTAThread()> _
Shared Sub Main()
' Add Global Exception Handler
AddHandler AppDomain.CurrentDomain.UnhandledException, _
AddressOf OnUnhandledException

Application.Run(New Form1)
End Sub

' In CF case only, ALL unhandled exceptions come here
Private Shared Sub OnUnhandledException(ByVal sender As Object, _
ByVal e As UnhandledExceptionEventArgs)
Dim ex As Exception = TryCast(e.ExceptionObject, Exception)
If (ex IsNot Nothing) Then
' Can't imagine e.IsTerminating ever being false
' or e.ExceptionObject not being an Exception
EntryPoint.HandleException(ex, e.IsTerminating)
End If
End Sub

'' This should not throw any exceptions
'' and should run as quick as possible
Private Shared Sub HandleException(ByVal ex As Exception, _
ByVal t As Boolean)
' Log ex.StackTrace or whatever
'MessageBox.Show(ex.StackTrace, ex.Message);
Dim fs As FileStream = Nothing
Dim sw As StreamWriter = Nothing
fs = New FileStream("GEH.txt", FileMode.Append, _
FileAccess.Write, FileShare.None, 1000, False)
sw = New StreamWriter(fs)
sw.WriteLine("DateStamp: " + DateTime.Now.ToString())
sw.WriteLine("ToString(): " + ex.ToString())
sw.WriteLine("Message: " + ex.Message)
sw.WriteLine("StackTrace: " + ex.StackTrace)
System.Threading.Thread.Sleep(1000) 'for a laugh
sw.WriteLine("THE END")
If sw IsNot Nothing Then
End If
End Try
End Sub
End Class

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