Powershell WinForms UI refresh / live update - multithreading

Question

I'm currently pulling my hair out trying to update a Winforms UI using the 'Register-objectevent' Cmdlet.
What I'm trying to do is get the Register-ObjectEvent to update the label in the form ever tick on the timer.
I've done hours of research on this, and I know it's something to do with multithreading / invoking, but I can't get my head around how to make it work !
If someone could show me / help me to get this script to update the label on the form by the timer, that would be amazing ! I've got lots of Winforms that would benifit from multithreading, but I need to get my head around it first !
Here's the script I'm trying to get working, any help is greatly appreciated :)
[reflection.assembly]::loadwithpartialname("System.Drawing") | Out-Null
[reflection.assembly]::loadwithpartialname("System.Windows.Forms") | Out-Null
[System.Windows.Forms.Application]::EnableVisualStyles() | out-null
$form1 = New-Object System.Windows.Forms.Form
$OnLoadForm_StateCorrection=
{
$form1.WindowState = $InitialFormWindowState
}
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Height = 600
$System_Drawing_Size.Width = 1200
$form1.ClientSize = $System_Drawing_Size
$form1.MaximizeBox = $False
$form1.DataBindings.DefaultDataSourceUpdateMode = 0
$form1.KeyPreview = $True
$form1.FormBorderStyle = 1
$form1.Name = "form1"
$form1.StartPosition = 1
$form1.backcolor = [System.Drawing.Color]::FromArgb(255,240,240,240)
$timer = New-Object System.Timers.Timer
$timer.Interval = 1000
$timer.AutoReset = $true
$timeout = 0
$num=0
$action = {
$num++
write-host "test"
$vollabel.text=$num
$timer.stop()
}
Register-ObjectEvent -InputObject $timer -SourceIdentifier TimerElapsed -EventName Elapsed -Action $action
$timer.start()
$vollabel = New-Object System.Windows.Forms.Label
$vollabel.Location = "0,0"
$form1.Controls.Add($vollabel)
$InitialFormWindowState = $form1.WindowState
$form1.add_Load($OnLoadForm_StateCorrection)
$form1.Add_Shown({$form1.Activate()})
$form1.ShowDialog()| Out-Null

Answer 1

I pared down your script a bit for a working proof of concept - add back in anything you needed:
#('System.Drawing','System.Windows.Forms') | %{ [reflection.assembly]::LoadWithPartialName($_) | Out-Null }
[System.Windows.Forms.Application]::EnableVisualStyles() | out-null
$form1 = New-Object System.Windows.Forms.Form -Property #{
MaximizeBox = $False
KeyPreview = $True
FormBorderStyle = 1
Name = "form1"
StartPosition = 1
backcolor = [System.Drawing.Color]::FromArgb(255,240,240,240)
ClientSize = New-Object System.Drawing.Size -Property #{Height = 600;Width = 1200}
}
$form1.DataBindings.DefaultDataSourceUpdateMode = 0
$timer = New-Object System.Windows.Forms.Timer -Property #{Interval = 1000} #Forms.Timer doesn't support AutoReset property
$script:num=0 #scope must be at script level to increment in event handler
$timer.start()
$timer.add_Tick({
$script:num +=1
write-host "test $script:num"
$vollabel.text=$script:num
})
$vollabel = New-Object System.Windows.Forms.Label -Property #{Location = "0,0"}
$form1.Controls.Add($vollabel)
$form1.ShowDialog()| Out-Null
$timer.stop() #This will keep running in the background unless you stop it
A few notes:
Form.ShowDialog() is blocking and stops the script execution.
System.Windows.Forms.Timer has slightly different properties than System.Timers.Timer and can take a ScriptBlock or a function name as a parameter to add_Tick()
An event handler ScriptBlock has its own scope, but you can share variables with the $ScopeName:VariableName syntax. I couldn't get $num to increment unless I set the scope to $Script