//File:Window.xaml.vb Imports System Imports System.Windows Imports System.Windows.Threading Namespace WpfApplication1 Public Partial Class Window1 Inherits Window Private timer As DispatcherTimer Public Sub New() InitializeComponent() End Sub Private Sub Button_Click(sender As Object, e As RoutedEventArgs) If timer Is Nothing OrElse Not timer.IsEnabled Then timer = New DispatcherTimer() timer.Interval = TimeSpan.FromMilliseconds(1000) AddHandler timer.Tick, New EventHandler(AddressOf timer_Tick) timer.Start() button.Content = "Stop Timer" Else timer.[Stop]() button.Content = "Start Timer" End If End Sub Private Sub timer_Tick(sender As Object, e As EventArgs) txtStatus.Text = DateTime.Now.Second.ToString() End Sub End Class End Namespace