Не работает событие left mouse button up

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.ComponentModel;
using System.Runtime.InteropServices;


namespace SilverlightApplication1
{
    public partial class MainPage : UserControl
    {
        Button btn1 = new Button();
        Button btn2 = new Button();

        public MainPage()
        {
            InitializeComponent();

            btn1.Content = "hello";
            btn1.Height = 30;
            btn1.Width = 70;
            btn1.MouseLeftButtonDown += new MouseButtonEventHandler(btn1_MouseLeftButtonDown);
            btn1.MouseEnter += new MouseEventHandler(btn1_MouseEnter);
            btn1.MouseRightButtonDown += new MouseButtonEventHandler(btn1_MouseRightButtonDown);
            btn1.MouseLeftButtonUp += new MouseButtonEventHandler(btn1_MouseLeftButtonUp);

            rootCanvas.Children.Add(btn1);


        }

        void btn1_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            MessageBox.Show("Left Btn UP");
        }

        void btn1_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
        {
            MessageBox.Show("Right Button Down");
        }

        void btn1_MouseEnter(object sender, MouseEventArgs e)
        {

        }

        void btn1_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            MessageBox.Show("Left Btn Down");
        }

    }