Trap and Windows Forms

Question

Hi, usually i have a  trap{} in my scripts to handle and log(!) all
unforseen exceptions which i have
not otherwise handled via Try/catch.
This works great.
But, when i have a script with windows forms, all exceptions will be displayed automatically as a system-popup
and the code inside trap{} is not executed, so the error never gets logged.
Why is the trap being ignored?
And how do i make my form execute the trap in case of an exception?
Thanks, Rob 
http://www.administrator.de/

Answer 1

Thanks for your reply David.
Separate runspace? Mhm, I dont think so. Otherwise I would not be able to access variables of the root script (that set up the form), would I? 
Also i do not set up confined script blocks to the events. They call functions in the script which call other functions and so on. Its
all one script, only that actions are triggered by events.
That depends on how the runspace is set up (and in this case, it's all being done by the PowerShell engine, so I'm not sure exactly what's happening.)  It's possible to give different runspaces access to the same variables, functions, etc (though you
have to be careful when doing that, as you may create race conditions.)
As I said, I don't know if that's actually what's happening here, but it would make sense.  Your main thread is blocking on $form1.ShowDialog(); until that function returns, execution would never jump to your trap block.
Anyhow, regardless of the technical details of why it's behaving this way, making sure you set up a new trap statement within those events (or the functions they call) does seem to work:
trap { Invoke-ErrorHandler -ErrorRecord $_ }
function Invoke-ErrorHandler
[CmdletBinding()]
param (
[Parameter(Mandatory = $true)]
[System.Management.Automation.ErrorRecord]
$ErrorRecord
Write-Host "This statement called from the error handler."
[void][System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
[System.Windows.Forms.Application]::EnableVisualStyles()
$form1 = New-Object 'System.Windows.Forms.Form'
$form1.ClientSize = '200, 150'
$button1 = New-Object 'System.Windows.Forms.Button'
$button1.Location = '54, 45'
$button1.Size = '75, 23'
$form1.Controls.Add($button1)
$button1.add_mouseclick({ TestFunction })
function TestFunction {
trap { Invoke-ErrorHandler -ErrorRecord $_ }
$button1.FalseProperty = 1
# TestFunction ## If you call the function here, instead of the command below, the trap catches the error
$form1.ShowDialog()