Powershell GUI pull downs populated by MS SQL table

I am generating a Powershell GUI with pull down menus. I am trying to populate these pull down menu's from a table in a SQL database. Within the pull down I want to be the value to be set by a table called 'AD_USERNAME' and displayname to be set by a table called 'DISPLAY_NAME'. I know how to display the contents on the screen but I'm not sure how to populate the pull downs?

I know I need to use Foreach to loop through the table but I can't work out how. I included the $name variables which I can use to print the table information on screen.

Here is the code I have so far -

$SQLServer = 'SQL1'
$SQLDBName = 'test'
$SqlQuery = 'select * from dbo.SMS_CONTACT'

$SqlConnection = New-Object System.Data.SqlClient.SqlConnection
$SqlConnection.ConnectionString = "Server = $SQLServer; Database = $SQLDBName; Integrated Security = True"

$SqlCmd = New-Object System.Data.SqlClient.SqlCommand
$SqlCmd.CommandText = $SqlQuery
$SqlCmd.Connection = $SqlConnection

$SqlAdapter = New-Object System.Data.SqlClient.SqlDataAdapter
$SqlAdapter.SelectCommand = $SqlCmd

$DataSet = New-Object System.Data.DataSet
$SqlAdapter.Fill($DataSet) | Out-Null
 
$SqlConnection.Close()

[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Drawing")
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")

$Form = New-Object System.Windows.Forms.Form    
$Form.Size = New-Object System.Drawing.Size(600,400)

$DropDownBox = New-Object System.Windows.Forms.ComboBox
$DropDownBox.Location = New-Object System.Drawing.Size(20,50)
$DropDownBox.Size = New-Object System.Drawing.Size(180,20)
$DropDownBox.DropDownHeight = 200
$DropDownBox.DropDownStyle = 2
$DropDownBox.Items.Add("$table")

$Form.Controls.Add($DropDownBox)

foreach ($Row in $DataSet.tables)
{
  $DropDownBox.Items.Add($Row)
  #$name = $Row.Item('AD_USERNAME'), $Row.Item('DISPLAY_NAME')
  #$name
}

$Form.Add_Shown({$Form.Activate()})
[void] $Form.ShowDialog()