Powershell Admin rights dont work in Windows Forms - powershell

Question

I want to add and remove user from the lokal Administrator group. Problem is that even I elevate rights in first place It still Access Denies me when I try to add them.
In a similar code It works this way... only thing I changed it that I created a GUI for it.
Here is the code:
$myWindowsID=[System.Security.Principal.WindowsIdentity]::GetCurrent()
$myWindowsPrincipal=new-object System.Security.Principal.WindowsPrincipal($myWindowsID)
$adminRole=[System.Security.Principal.WindowsBuiltInRole]::Administrator
if (!$myWindowsPrincipal.IsInRole($adminRole)){
start-process "powershell" -Verb "runas" -ArgumentList "-File",$MyInvocation.MyCommand.Definition
}
[VOID] [System.Reflection.Assembly]::LoadWithPartialName("System.Drawing")
[Void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
$objForm = New-Object System.Windows.Forms.Form
$objForm.BackgroundImageLayout = 0
$objForm.BackgroundImage =[System.Drawing.Image]::FromFile('xx')
$objForm.StartPosition = "CenterScreen"
$objForm.Icon="xx"
$objForm.Size = New-Object System.Drawing.Size(400,200)
$objForm.Text = "Lokal Admin Adder v.01"
$objLabel = New-Object System.Windows.Forms.Label
$objLabel.Location = New-Object System.Drawing.Size(75,30)
$objLabel.Size = New-Object System.Drawing.Size(240,20)
$objLabel.Text = "Nutzernamen eingeben(m_mustermann)"
$objForm.Controls.Add($objLabel)
$objLabel2 = New-Object System.Windows.Forms.Label
$objLabel2.Location = New-Object System.Drawing.Size(280,140)
$objLabel2.Size = New-Object System.Drawing.Size(300,20)
$objLabel2.Text = "by Lucas Klarner"
$objForm.Controls.Add($objLabel2)
$objTextBox = New-Object System.Windows.Forms.TextBox
$objTextBox.Location = New-Object System.Drawing.Size(85,50)
$objTextBox.Size = New-Object System.Drawing.Size(200,20)
$objForm.Controls.Add($objTextBox)
$FinishButton = New-Object System.Windows.Forms.Button
$FinishButton.Location = New-Object System.Drawing.Size (20,80)
$FinishButton.Size = New-Object System.Drawing.Size (150,20)
$FinishButton.Text = "Nutzer hinzufügen"
$FinishButton.Name = "Nutzer hinzufügen"
$FinishButton.Add_Click({
$Usr = $objTextBox.Text; Add-LocalGroupMember -Group Administratoren -Member $Usr })
$objForm.Controls.Add($FinishButton)
$DeleteButton = New-Object System.Windows.Forms.Button
$DeleteButton.Location = New-Object System.Drawing.Size (210,80)
$DeleteButton.Size = New-Object System.Drawing.Size (150,20)
$DeleteButton.Text = "Nutzer entfernen"
$DeleteButton.Name = "Nutzer entfernen"
$DeleteButton.DialogResult = "OK"
$DeleteButton.Add_Click({
$Usr = $objTextBox.Text;Remove-LocalGroupMember -Group Administratoren -Member $Usr -Verbose })
$objForm.Controls.Add($DeleteButton)
[void] $objForm.ShowDialog()
Thanks a lot!!

Answer 1

FIXED:
Somehow my elevation code was not running correctly and I made a new one out of some internet posts:
if (-Not ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] 'Administrator')) {
if ([int](Get-CimInstance -Class Win32_OperatingSystem | Select-Object -ExpandProperty BuildNumber) -ge 6000) {
$CommandLine = "-File `"" + $MyInvocation.MyCommand.Path + "`" " + $MyInvocation.UnboundArguments
Start-Process -FilePath PowerShell.exe -Verb Runas -ArgumentList $CommandLine
Exit
}
}
Here's how it works:
The first line checks to see if the script is already running in an elevated environment. This would occur if PowerShell is running as Administrator or UAC is disabled. If it is, the script will continue to run normally in that process.
The second line checks to see if the Windows operating system build number is 6000 (Windows Vista) or greater. Earlier builds did not support Run As elevation.
The third line retrieves the command line used to run the original script, including any arguments.
Finally, the fourth line starts a new elevated PowerShell process where the script runs again. Once the script terminates, the elevated PowerShell window closes.
https://blog.expta.com/2017/03/how-to-self-elevate-powershell-script.html