How do I add an event handler to a .NET object in PowerShell?

Question

I'm writing a PowerShell script which uses a third-party library. One of the objects I'm using requires that I add an event handler. The event delegate looks like this:

public delegate void TSBPGPCreateOutputStreamEvent(object Sender, 
                                                   string Filename, 
                                                   System.DateTime TimeStamp, 
                                                   ref System.IO.Stream Stream, 
                                                   ref bool FreeOnExit)

In PowerShell, I tried doing this:

$reader.Add_OnCreateOutputStream( {
    param(
        $sender,
        $fileName,
        $timestamp,
        [ref]
        $stream,
        [ref]
        $freeOnExit
    )
    $stream = New-Object IO.MemoryStream
} )

But I get back this error message:

 Cannot convert value "
    param(
        $sender,
        $fileName,
        $timestamp,
        [ref]
        $stream,
        [ref]
        $freeOnExit
    )
$stream = New-Object IO.MemoryStream
" to type "SBPGP.TSBPGPCreateOutputStreamEvent". 
Error: "The type 'System.IO.Stream&' may not be used as a type argument."

Is there a better way of subscribing to events? Why can't the Stream type be used as a type argument? What am I doing wrong?

Bas Bossink · Accepted Answer · 2012-09-13 13:13:24Z

10

You should use the Register-ObjectEvent cmdlet, take a look at the examples on your own system by using:

PS> Get-Help Register-ObjectEvent -full

answered Sep 13, 2012 at 13:13

Bas Bossink

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laddie · Accepted Answer · 2013-09-05 01:45:09Z

4

Add-Type -AssemblyName System.Windows.Forms
[reflection.assembly]::loadwithpartialname("System.Drawing") | Out-Null
$form = New-Object Windows.Forms.Form
$form.add_mousedown($handler_form_mousedown)
$handler_form_Mousedown=
{
param([object]$sender, [System.EventArgs]$e)
write-host $e.x
write-host $e.y
$sender.text="if ya think your so noble answer the question"
$sender.text = "Nobles Oblige"
# PS HELP IS USELESS FOR THIS    
}

$App = $form.ShowDialog()

answered Sep 5, 2013 at 1:45

laddie

911 bronze badge

2 Comments

Alex Over a year ago

This is actually the correct, working answer. In my case, I needed to add event handlers to a list of LinkLabel WinForm controls within PowerShell where each LinkLabel needed to access its own Tag property inside the event handler. The info provided in this answer was the only way to accomplish that.

greatvovan Over a year ago

I tried to use this approach to add a handler for SqlConnection.InfoMessage event and it works only partially. By this I mean that the handler is invoked not when the event triggers (on messages coming from the database), but instead all events are handled in the end, after finishing SqlCommand.ExecuteNonQuery(). Any idea why?

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