Store credentials on button - winforms

Question

To make it easier for new employees to connect to Exchange via powershell im writting a quick little tools using powershell:winforms.
The tool will just contain a couple of buttons, text field, en informative text so users can manage the Exchange envoirement from one UI.
#1 Set Credentials Button
$Set_Credential = New-Object System.Windows.Forms.Button
$Set_Credential.Top = "5"
$Set_Credential.Left = "5"
$Set_Credential.Anchor = "Left,Top"
$Set_Credential.Text = 'Set Credentials'
$Set_Credential.add_Click({
$UserCredential = Get-Credential
})
$Exchange_Manager.Controls.Add($Set_Credential)
#3 Connect to Exchange Online
$Exchange_Connect = New-Object System.Windows.Forms.Button
$Exchange_Connect.Top = "5"
$Exchange_Connect.Left = "150"
$Exchange_Connect.Anchor ="Left,Top"
$Exchange_Connect.Text = 'Connect'
$Exchange_Connect.add_Click({
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential "$UserCredential" -Authentication Basic -AllowRedirection
Import-PSSession $Session
})
$Exchange_Manager.Controls.Add($Exchange_Connect)
As you can see the first 'Set Credentials' button allows for users to enter credentials via the default get-credentials.
The Second button 'Connect to Exchange' starts a new PSSession using the $UserCredentials to login.
The issue i'm facing is that when pressing the connect button i get an error that says the -credential value is Null.
Querying the $UserCredential also gives an empty line.
It seems that altrough the credentials get entered they dont get stored because they are called trough an button function.
I tried looking it up but most of the anwsers are quite vague.
Ful code:
Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
$Exchange_Manager = New-Object Windows.Forms.Form
#Session Initation 1
#1 Set Credentials Button
$Set_Credential = New-Object System.Windows.Forms.Button
$Set_Credential.Top = "5"
$Set_Credential.Left = "5"
$Set_Credential.Anchor = "Left,Top"
$Set_Credential.Text = 'Set Credentials'
$Set_Credential.add_Click({
$UserCredential = Get-Credential
})
$Exchange_Manager.Controls.Add($Set_Credential)
#2 Current Credentials
#3 Connect to Exchange Online
$Exchange_Connect = New-Object System.Windows.Forms.Button
$Exchange_Connect.Top = "5"
$Exchange_Connect.Left = "150"
$Exchange_Connect.Anchor ="Left,Top"
$Exchange_Connect.Text = 'Connect'
$Exchange_Connect.add_Click({
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential "$UserCredential" -Authentication Basic -AllowRedirection
Import-PSSession $Session
})
$Exchange_Manager.Controls.Add($Exchange_Connect)
#Information
#1 Set Credentials Button
$Mailboxes = New-Object System.Windows.Forms.Button
$Mailboxes.Top = "50"
$Mailboxes.Left = "5"
$Mailboxes.Anchor = "Left,Top"
$Mailboxes.Text = 'Get All Mailboxes'
$Mailboxes.add_Click({
Get-Mailbox |Select-Object DisplayName, Alias | Sort-Object -Property DisplayName | Out-gridview
})
$Exchange_Manager.Controls.Add($Mailboxes)
$Exchange_Manager.ShowDialog()

Answer 1

You need to make $UserCredential a global.
Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
$Exchange_Manager = New-Object Windows.Forms.Form
$Exchange_Manager.TopMost = $true
# create a global empty credential object
$Global:UserCredential = [System.Management.Automation.PSCredential]::Empty
#Session Initation 1
#1 Set Credentials Button
$Set_Credential = New-Object System.Windows.Forms.Button
$Set_Credential.Top = "5"
$Set_Credential.Left = "5"
$Set_Credential.Anchor = "Left,Top"
$Set_Credential.Text = 'Set Credentials'
$Set_Credential.add_Click({
$Global:UserCredential = Get-Credential
})
$Exchange_Manager.Controls.Add($Set_Credential)
#2 Current Credentials
#3 Connect to Exchange Online
$Exchange_Connect = New-Object System.Windows.Forms.Button
$Exchange_Connect.Top = "5"
$Exchange_Connect.Left = "150"
$Exchange_Connect.Anchor ="Left,Top"
$Exchange_Connect.Text = 'Connect'
$Exchange_Connect.add_Click({
if ($Global:UserCredential -ne [System.Management.Automation.PSCredential]::Empty) {
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential "$Global:UserCredential" -Authentication Basic -AllowRedirection
Import-PSSession $Session
}
})
$Exchange_Manager.Controls.Add($Exchange_Connect)
#4 Show the dialog and dispose of it afterwards
$Exchange_Manager.ShowDialog()
$Exchange_Manager.Dispose()