<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <Grid>
        <Button Height="23" Margin="95,0,108,45" Name="button1" VerticalAlignment="Bottom" Click="button1_Click">Button</Button>
        <TextBlock Margin="38,40,19,88" Name="textBlock1" />
    </Grid>
</Window>

    public partial class Window1 : Window
    {
        private delegate void DeleDoWork();

        public Window1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            DeleDoWork work = new DeleDoWork(DoWork);
            Dispatcher.BeginInvoke(work);
        }

        private void DoWork()
        {
            for (int i = 0; i < 100; i++)
            {
                textBlock1.Text = i.ToString();
                Thread.Sleep(200);
            }
        }
    }