问SDK windows phone C# random.Next()；

EN

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Net;
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Navigation;
    using Microsoft.Phone.Controls;
    using Microsoft.Phone.Shell;
    using System.Windows.Threading;
    using System.Windows.Media.Imaging;


    namespace madAssignment
    {
        public partial class gamePlay : PhoneApplicationPage
        {
            int counter = 1000000;
            DispatcherTimer timer;

            int count = 0;

            public gamePlay()
            {
                InitializeComponent();

                timer = new DispatcherTimer();
                timer.Interval = TimeSpan.FromSeconds(0.1);
                timer.Tick += timer_Tick;
                // Sample code to localize the ApplicationBar
                //BuildLocalizedApplicationBar();
            }

            void timer_Tick(object sender, EventArgs e)
            {
                //int num;
                counter -= 1;
                txtCount.Text = counter.ToString();

                if(Convert.ToInt32(txtCount.Text) == 0)
                {
                    timer.Stop();

                    Uri uri = new Uri("/gameEnd.xaml", UriKind.Relative);
                    this.NavigationService.Navigate(uri);
                }
            }

    int rand()
    {
        Random r = new Random();

        int p = 1;

        if(p == 0)
        {
            imgLeft.Visibility = Visibility.Visible;
            imgRight.Visibility = Visibility.Collapsed;
        }
        else
        {
            imgLeft.Visibility = Visibility.Collapsed;
            imgRight.Visibility = Visibility.Visible;
        }

        int i = r.Next(0, 2);

        return i;
    }

    private void btnTimerStart_Tap(object sender, System.Windows.Input.GestureEventArgs e)
    {
        imgLeft.Visibility = Visibility.Collapsed;
        imgRight.Visibility = Visibility.Collapsed;

        timer.Start();

        rand();

    }

    private void btnLeft_Tap(object sender, System.Windows.Input.GestureEventArgs e)
    {
        if (rand() == 0)
        {
            count += 1;
            txtScore.Text = count.ToString();
        }
        else
        {
            count -= 1;
            txtScore.Text = count.ToString();
        }
    }

    private void btnRight_Tap(object sender, System.Windows.Input.GestureEventArgs e)
    {
        if(rand() == 1)
        {
            count += 1;
            txtScore.Text = count.ToString();
        }
        else
        {
            count -= 1;
            txtScore.Text = count.ToString();
        }
    }
}