Can't make C# in PowerShell COM visible using HTML

Question

Im making a web app that turns of computer everytime its not visible to COM (component object model)

Exception setting "ObjectForScripting": "ObjectForScripting's class must be visible to COM. Verify that the object is public, or consider adding the ComVisible attribute to your class." At C:\Users\kayde\window.ps1:99 char:1

$webBrowser.ObjectForScripting = $scriptBlock

  + CategoryInfo          : NotSpecified: (:) [], SetValueInvocationException
  + FullyQualifiedErrorId : ExceptionWhenSetting

I tried using C#:

Add-Type -AssemblyName System.Windows.Forms

# Define the .NET class directly in PowerShell with ComVisible attribute
$scriptBlock = {
    Add-Type @"
    using System;
    using System.Runtime.InteropServices;

    [ComVisible(true)]
    public class ActionHandler
    {
        public void HandleAction(string action)
        {
            switch (action)
            {
                case "PowerOff":
                    System.Diagnostics.Process.Start("shutdown.exe", "/s /f /t 0");
                    break;
                case "Reboot":
                    System.Diagnostics.Process.Start("shutdown.exe", "/r /f /t 0");
                    break;
                case "Restart":
                    System.Diagnostics.Process.Start("shutdown.exe", "/r /f /t 0");
                    break;
            }
        }
    }
"@ -PassThru
}

# Create the form
$form = New-Object System.Windows.Forms.Form
$form.Text = "Power options"
$form.MaximumSize = New-Object System.Drawing.Size(300, 240)
$form.Size = New-Object System.Drawing.Size(250, 180) 
$form.MinimumSize = New-Object System.Drawing.Size(250, 180)
$form.ShowIcon = $false

# Create the WebBrowser control
$webBrowser = New-Object System.Windows.Forms.WebBrowser
$webBrowser.Dock = [System.Windows.Forms.DockStyle]::Fill

# Load HTML content into the WebBrowser control
$htmlContent = @"
<!DOCTYPE html>
<html>
<head>
    <title>Power options</title>
</head>
<body>

    <button id="a">
        Power
    </button><br>
    <button id="b">
        Reboot
    </button><br>
    <button id="c">
        Restart
    </button><br>
    <style>
        body {
            font-family: Verdana, Geneva, Tahoma, sans-serif;
            background-color: black;
        }

        button {
            color: blue;
            background-color: black;
            border: 1px solid blue;
            margin-left: 8px;
        }
    </style>
    <script>
        // Function to send message to PowerShell script
        function sendAction(action) {
            window.external.HandleAction(action);
        }

        // Attach click event handlers to the buttons
        document.getElementById("a").attachEvent("onclick", function() {
            sendAction("PowerOff");
        });

        document.getElementById("b").attachEvent("onclick", function() {
            sendAction("Reboot");
        });

        document.getElementById("c").attachEvent("onclick", function() {
            sendAction("Restart");
        });
    </script>
</body>
</html>
"@

# Set the HTML content and object for scripting for the WebBrowser control
$webBrowser.DocumentText = $htmlContent
$webBrowser.ObjectForScripting = $scriptBlock

# Add the WebBrowser control to the form
$form.Controls.Add($webBrowser)

# Show the form
$form.ShowDialog() | Out-Null

maybe instead of using COM I could use ICP(inter communication protocol)

I tried and was expecting it to power of computer on windows 11

Why are you assigning $scriptBlock to $webBrowser.ObjectForScripting? Sounds like you'll want to execute the scriptblock, and then create and pass an instance of the ActionHandler type instead (eg. $webBrowser.ObjectForScripting = (&$scriptBlock)::new()) — Mathias R. Jessen
– Mathias R. Jessen, Commented Apr 2, 2024 at 16:59

Mathias R. Jessen · Accepted Answer · 2024-04-02 17:05:13Z

1

As hinted in the comments, the problem here is that you're assigning an object of type [scriptblock] to $webBrowser.ObjectForScripting.

My guess is that you'll want to assign an instance of the ActionHandler class instead - so invoke the scriptblock to compile the type, then create an instance and assign that:

# invoke scriptblock, store resulting type
$handlerType = & $scriptBlock

# create a new instance of the ActionHandler type
$myActionHandler = $handlerType::new()

# assign to target property
$webBrowser.ObjectForScripting = $myActionHandler

answered Apr 2, 2024 at 17:05

Mathias R. Jessen

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