изучение PowerShell и попытка получить значение из текстового поля

Я новичок в этом, и я пытаюсь создать графический интерфейс Powershell с полем текстового поля и использовать текст для запроса AD. Что-то не так с моим кодом. Текст хранится в переменных $textbox_HelloWorld. Текст и вызывается в обработчике событий $button_ClickMe.Add_Click. Это не возвращает никаких результатов. Если я заменю переменную строкой, она сработает. Похоже, проблема в области видимости, но я пробовал использовать $script: и $global, но ни один из них не работал.

Любая помощь оценили.

# import AD module
import-module activedirectory

# Load required assemblies
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")


# Drawing form and controls
$Form_HelloWorld = New-Object System.Windows.Forms.Form
    $Form_HelloWorld.Text = "Hello World"
    $Form_HelloWorld.Size = New-Object System.Drawing.Size(480,240)
    $Form_HelloWorld.FormBorderStyle = "FixedDialog"
    $Form_HelloWorld.TopMost = $true
    $Form_HelloWorld.MaximizeBox = $false
    $Form_HelloWorld.MinimizeBox = $false
    $Form_HelloWorld.ControlBox = $true
    $Form_HelloWorld.StartPosition = "CenterScreen"
    $Form_HelloWorld.Font = "Segoe UI"


# adding firstName TextBox to my form
$textbox_HelloWorld = New-Object System.Windows.Forms.TextBox
    $textbox_HelloWorld.Location = New-Object System.Drawing.Size(8,4)
    $textbox_HelloWorld.Size = New-Object System.Drawing.Size(120,32)
    $textbox_HelloWorld.TextAlign = "MiddleCenter"
    $global:textbox_HelloWorld.Text = "Enter first name!"
    $Form_HelloWorld.Controls.Add($textbox_HelloWorld)
    $firstnme=$textbox_HelloWorld.Text


# adding firstName label to my form
$label_HelloWorld = New-Object System.Windows.Forms.Label
    $label_HelloWorld.Location = New-Object System.Drawing.Size(128,4)
    $label_HelloWorld.Size = New-Object System.Drawing.Size(80,16)
    $label_HelloWorld.TextAlign = "MiddleCenter"
    $label_HelloWorld.Text = "First Name"
    $Form_HelloWorld.Controls.Add($label_HelloWorld)

# adding lastName TextBox to my form
$Secondtextbox_HelloWorld = New-Object System.Windows.Forms.TextBox
    $Secondtextbox_HelloWorld.Location = New-Object System.Drawing.Size(8,38)
    $Secondtextbox_HelloWorld.Size = New-Object System.Drawing.Size(120,32)
    $Secondtextbox_HelloWorld.TextAlign = "MiddleCenter"
    $global:Secondtextbox_HelloWorld.Text = "Enter last name!"
    $Form_HelloWorld.Controls.Add($Secondtextbox_HelloWorld)
    $lastnme=$Secondtextbox_HelloWorld.Text


# adding lastName label to my form
$Secondlabel_HelloWorld = New-Object System.Windows.Forms.Label
    $Secondlabel_HelloWorld.Location = New-Object System.Drawing.Size(128,38)
    $Secondlabel_HelloWorld.Size = New-Object System.Drawing.Size(80,16)
    $Secondlabel_HelloWorld.TextAlign = "MiddleCenter"
    $Secondlabel_HelloWorld.Text = "Last Name"
    $Form_HelloWorld.Controls.Add($Secondlabel_HelloWorld)

# add a button
$button_ClickMe = New-Object System.Windows.Forms.Button
    $button_ClickMe.Location = New-Object System.Drawing.Size(8,80)
    $button_ClickMe.Size = New-Object System.Drawing.Size(240,32)
    $button_ClickMe.TextAlign = "MiddleCenter"
    $button_ClickMe.Text = "Click Me!"
    $button_ClickMe.Add_Click({
        $button_ClickMe.Text = "Submitted"
        $nme = Get-ADUser -Filter "GivenName -like '$global:textbox_HelloWorld.Text' -and Surname -like '$global:Secondtextbox_HelloWorld.Text*'" | Select-Object -ExpandProperty SamAccountName | out-string
        [System.Windows.Forms.MessageBox]::Show($nme , "My Dialog Box")
    })

    $Form_HelloWorld.Controls.Add($button_ClickMe)

# show form
$Form_HelloWorld.Add_Shown({$Form_HelloWorld.Activate()})
[void] $Form_HelloWorld.ShowDialog()