//File:Window.xaml.vb Imports System.Linq Imports System.Windows Imports System.Windows.Controls Namespace WpfApplication1 Public Partial Class Window1 Inherits Window Public Sub New() InitializeComponent() End Sub Private Sub Button_Click(sender As Object, e As RoutedEventArgs) listbox.Items.Clear() For Each checkbox As CheckBox In panel.Children.OfType(Of CheckBox)().Where(Function(cb) cb.IsChecked = True) listbox.Items.Add(checkbox.Name) Next End Sub Private Sub CheckBox_Unchecked(sender As Object, e As RoutedEventArgs) If Not IsInitialized Then Return End If Dim checkbox As CheckBox = TryCast(e.OriginalSource, CheckBox) If checkbox IsNot Nothing Then MessageBox.Show(checkbox.Name & " is unchecked.", Title) End If End Sub End Class End Namespace