PowerShell Cmdlet Deep Dive: Add-Type

Welcome back to Wahmans PowerShell Blog! Today we’ll explore a mighty and often underutilized cmdlet: Add-Type. This command lets you bring the power of .NET into your PowerShell scripts by adding a .NET class to your PowerShell session.

Microsoft’s Official Description: Adds a Microsoft .NET class to a PowerShell session.

This foundational capability can be used to extend your scripts with performance-optimized or specialized functionality not provided by PowerShell out of the box. Let’s look at how to use Add-Type in several practical scenarios — from beginner to more advanced use cases.

Example 1: Creating a Simple .NET Class

This example shows how to create and use a simple C# class directly within PowerShell.

$classDefinition = @"
public class Greeter {
    public string SayHello(string name) {
        return $"Hello, {name}!";
    }
}
"@

Add-Type -TypeDefinition $classDefinition
$greeter = New-Object Greeter
$greeter.SayHello("Alice")

Explanation: You’re defining a class called Greeter with a method SayHello and calling it via PowerShell.

Example 2: Generate a Random Number Using .NET’s Random Class

PowerShell has its own ways for generating random numbers, but here’s how to do it using .NET via Add-Type.

Add-Type -AssemblyName System
$random = New-Object System.Random
$random.Next(1, 100)

Explanation: Using Add-Type allows access to the broader .NET Base Class Library, like System.Random.

Example 3: Create Custom Windows Forms with .NET

PowerShell doesn’t natively support GUI, but Add-Type allows you to build it using Windows Forms. Here, we create a basic form with a button:

Add-Type -AssemblyName System.Windows.Forms

$form = New-Object System.Windows.Forms.Form
$form.Text = "My First Form"
$form.Width = 300
$form.Height = 200

$button = New-Object System.Windows.Forms.Button
$button.Text = "Click Me"
$button.Width = 100
$button.Height = 50
$button.Top = 50
$button.Left = 100

$button.Add_Click({ [System.Windows.Forms.MessageBox]::Show("Hello from PowerShell!") })

$form.Controls.Add($button)
$form.ShowDialog()

Explanation: A quick way to add a basic GUI to your scripts using the Windows Forms .NET library.

Example 4: Using Add-Type to Call Native Win32 API

This more advanced example demonstrates calling a Windows API to perform an operation outside of built-in PowerShell functionality.

$signature = @"
using System;
using System.Runtime.InteropServices;

public class User32 {
    [DllImport("user32.dll")] public static extern bool LockWorkStation();
}
"@

Add-Type -TypeDefinition $signature
[User32]::LockWorkStation()

Explanation: You declared and used a native function (LockWorkStation) from user32.dll to lock the PC. This unlocks (pun intended) a world of low-level OS functionalities from within PowerShell.

Wrapping Up

Add-Type might look simple at first, but it gives you unmatched flexibility by letting you seamlessly blend .NET with PowerShell. Whether you want to write quick ad-hoc classes, create GUIs, or tap into native Windows APIs, Add-Type is your gateway.

Happy scripting, and I will see you in the next post!