ComboBox.SelectedItem is null - powershell

Question

I populated a combobox with AD SamAccountName items. When selecting one of the items, one can push a button in order to retrieve information from that account. However, when clicking the button I receive the below error:
Cannot validate argument on parameter 'Identity'. The argument is null. Provide a valid value for the argument, and then try running the command again.
The command the error refers to is:
$Label_User_ItemContent.Text = (Get-ADUser -Identity $ComboBox.SelectedItem).SamAccountName
The crucial part of the code is:
$ComboBox = New-Object -TypeName System.Windows.Forms.ComboBox
$ComboBox.Width = 300
$ComboBox.Location = New-Object -TypeName System.Drawing.Point(250, 25)
$Users = Get-ADUser -Filter * | Where-Object {$_.SamAccountName -match '^adminA'}
ForEach ($User in $Users){
$ComboBox.Items.Add($User.SamAccountName)
}
$ComboBox.SelectedIndex = 1
$MainWindow.Controls.Add($ComboBox)
$Button_Check_TEST = New-Object -TypeName System.Windows.Forms.Button
$Button_Check_TEST.Location = New-Object -TypeName System.Drawing.Size(350, 150)
$Button_Check_TEST.Size = New-Object -TypeName System.Drawing.Size(150, 50)
$Button_Check_TEST.Text = 'Check'
$MainWindow.Controls.Add($Button_Check_TEST)
$Button_Check_TEST.Add_Click({
Try{
$Label_User_ItemContent.Text = (Get-ADUser -Identity $ComboBox.SelectedItem).SamAccountName
}
Catch{
Write-Verbose -Verbose $_.Exception.Message
}
})
The problem is, that I need two layers. Basically, there should be a menu with four different options, one of them is 'User'. When clicking on 'User' the ComboBox and the 'Click'-Button shall appear.
Using the code above without the 'User'-Button works fine.
Question: Why does the ComboBox.SelectedItem not work when I use a button to 'create' the ComboBox?
The complete code is below:
$font = New-Object -TypeName System.Drawing.Font("Times New Roman", 18, [System.Drawing.FontStyle]::Bold)
$MainWindow = New-Object -TypeName System.Windows.Forms.Form
$MainWindow.Text = 'PIM v10 Administrator Window'
$MainWindow.Width = 600
$MainWindow.Height = 555
$MainWindow.AutoSize = $true
$Button_User = New-Object -TypeName System.Windows.Forms.Button
$Button_User.Location = New-Object -TypeName System.Drawing.Size(25, 25)
$Button_User.Size = New-Object -TypeName System.Drawing.Size(200, 75)
$Button_User.Text = 'User'
$Button_User.Font = $font
$MainWindow.Controls.Add($Button_User)
$Button_User.Add_Click({
$Label_User = New-Object -TypeName System.Windows.Forms.Label
$Label_User.Text = 'Given Name:'
$Label_User.Location = New-Object -TypeName System.Drawing.Point(250, 50)
$Label_User.AutoSize = $true
$MainWindow.Controls.Add($Label_User)
$Label_User_ItemContent = New-Object -TypeName System.Windows.Forms.Label
$Label_User_ItemContent.Text = ''
$Label_User_ItemContent.Location = New-Object -TypeName System.Drawing.Point(250, 100)
$MainWindow.Controls.Add($Label_User_ItemContent)
$ComboBox = New-Object -TypeName System.Windows.Forms.ComboBox
$ComboBox.Width = 300
$ComboBox.Location = New-Object -TypeName System.Drawing.Point(250, 25)
$Users = Get-ADUser -Filter * | Where-Object {$_.SamAccountName -match '^adminA'}
ForEach ($User in $Users){
$ComboBox.Items.Add($User.SamAccountName)
}
$ComboBox.SelectedIndex = 1
$MainWindow.Controls.Add($ComboBox)
$Button_Check_TEST = New-Object -TypeName System.Windows.Forms.Button
$Button_Check_TEST.Location = New-Object -TypeName System.Drawing.Size(350, 150)
$Button_Check_TEST.Size = New-Object -TypeName System.Drawing.Size(150, 50)
$Button_Check_TEST.Text = 'Check'
$MainWindow.Controls.Add($Button_Check_TEST)
$Button_Check_TEST.Add_Click({
Try{
$Label_User_ItemContent.Text = (Get-ADUser -Identity $ComboBox.SelectedItem).SamAccountName
}
Catch{
Write-Verbose -Verbose $_.Exception.Message
}
})
if (-not ($ComboBox.SelectedItem -eq $null)){
$Label_User_ItemContent.Text = (Get-ADUser -Identity $ComboBox.SelectedItem).SamAccountName
}
else {
Write-Host -Object "Object is null"
}
})
$MainWindow.ShowDialog()

Answer 1

So whats happening is you are creating variables in the wrong scope
$Button_User.Add_Click({
$ComboBox = New-Object -TypeName System.Windows.Forms.ComboBox
$Label_User_ItemContent = New-Object -TypeName System.Windows.Forms.Label
$MainWindow.Controls.Add($ComboBox)
$Label_User_ItemContent = New-Object -TypeName System.Windows.Forms.Label
$Button_Check_TEST.Add_Click({
$Label_User_ItemContent.Text = (Get-ADUser -Identity
$ComboBox.SelectedItem).SamAccountName
)}
})
Since you are creating the Combo and the Lable inside a Add_click action. Those Values only exist when the action is taken and in the $MainWindows.Controls. The items are then cleared from memory
When you run the next action $Button_Check_TEST.Add_Click() since the variables are cleared then $ComboBox and $Label_User_ItemContent equal nothing.
A fix would be to place them outside the $Button_User.Add_Click() event
$ComboBox = New-Object -TypeName System.Windows.Forms.ComboBox
$Label_User_ItemContent = New-Object -TypeName System.Windows.Forms.Label
$Button_User.Add_Click({
$MainWindow.Controls.Add($ComboBox)
$Label_User_ItemContent = New-Object -TypeName System.Windows.Forms.Label
$Button_Check_TEST.Add_Click({
$Label_User_ItemContent.Text = (Get-ADUser -Identity
$ComboBox.SelectedItem).SamAccountName
)}
})
Here is the whole script in working condition now
$font = New-Object -TypeName System.Drawing.Font("Times New Roman", 18, [System.Drawing.FontStyle]::Bold)
$MainWindow = New-Object -TypeName System.Windows.Forms.Form
$MainWindow.Text = 'PIM v10 Administrator Window'
$MainWindow.Width = 600
$MainWindow.Height = 555
$MainWindow.AutoSize = $true
$Button_User = New-Object -TypeName System.Windows.Forms.Button
$Button_User.Location = New-Object -TypeName System.Drawing.Size(25, 25)
$Button_User.Size = New-Object -TypeName System.Drawing.Size(200, 75)
$Button_User.Text = 'User'
$Button_User.Font = $font
$MainWindow.Controls.Add($Button_User)
$ComboBox = New-Object -TypeName System.Windows.Forms.ComboBox
$Label_User_ItemContent = New-Object -TypeName System.Windows.Forms.Label
$Button_User.Add_Click({
$Label_User = New-Object -TypeName System.Windows.Forms.Label
$Label_User.Text = 'Given Name:'
$Label_User.Location = New-Object -TypeName System.Drawing.Point(250, 50)
$Label_User.AutoSize = $true
$MainWindow.Controls.Add($Label_User)
$Label_User_ItemContent.Text = ''
$Label_User_ItemContent.Location = New-Object -TypeName System.Drawing.Point(250, 100)
$MainWindow.Controls.Add($Label_User_ItemContent)
$ComboBox.Width = 300
$ComboBox.Location = New-Object -TypeName System.Drawing.Point(250, 25)
$Users = Get-ADUser -Filter * | Where-Object {$_.SamAccountName -match '^adminA'}
$MainWindow.Controls.Add($ComboBox)
ForEach ($User in $Users){
$ComboBox.Items.Add($User.SamAccountName)
}
$MainWindow.Controls.Add($ComboBox)
$ComboBox.SelectedIndex = 0
$Button_Check_TEST = New-Object -TypeName System.Windows.Forms.Button
$Button_Check_TEST.Location = New-Object -TypeName System.Drawing.Size(350, 150)
$Button_Check_TEST.Size = New-Object -TypeName System.Drawing.Size(150, 50)
$Button_Check_TEST.Text = 'Check'
$MainWindow.Controls.Add($Button_Check_TEST)
$Button_Check_TEST.Add_Click({
Try{
$Label_User_ItemContent.Text = (Get-ADUser -Identity $ComboBox.SelectedItem).SamAccountName
}
Catch{
Write-Verbose -Verbose $_.Exception.Message
}
})
if (-not ($ComboBox.SelectedItem -eq $null)){
$Label_User_ItemContent.Text = (Get-ADUser -Identity $ComboBox.SelectedItem).SamAccountName
}
else {
Write-Host -Object "Object is null"
}
})
$MainWindow.ShowDialog()