silverlight DispatcherTimer 使按钮在指定的时间内不可编辑

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Threading;


namespace SilverlightApplication39
{
    public partial class MainPage : UserControl
    {
        private Button TestButton = null;
        private dispatcherTimer timer = null;
        public MainPage()
        {
            InitializeComponent();
            TestButton = new Button();
            TestButton.Width = 200;
            TestButton.Height = 24;
            TestButton.Content = "Test";
            TestButton.Click += new RoutedEventHandler(TestButton_Click);
            LayoutRoot.Children.Add(TestButton);


            timer = new dispatcherTimer();
            timer.Interval = new TimeSpan(0,2);
            timer.Tick += new EventHandler(timer_Tick);
        }
        void timer_Tick(object sender,EventArgs e)
        {
            TestButton.IsEnabled = true;
        }
        void TestButton_Click(object sender,RoutedEventArgs e)
        {
            TestButton.IsEnabled = false;
            timer.Start();
        }
    }
}