Question

I am writting minesweeper game in c# silverlight.
1. How can I add a counter (counting seconds only) to this application?
2. How can I stop counter when application goes to the background (middle button, search button, incoming call etc.)?
3. How can I do something when WP7 is closing my application process? For example save current game to isolated storage.

Answer 1

1) You need to use Timer

        timer.Tick += new EventHandler(timer_Tick); // Everytime timer ticks, timer_Tick will be called
        timer.Interval = (1000) * (10);             // Timer will tick evert 10 seconds
        timer.Enabled = true;                       // Enable the timer
        timer.Start();                              // Start the time

void timer_Tick(object sender, EventArgs e)
        {
           //Do something
        }

2) You need to handle OnNavigatedFrom Event:

private void Application_Deactivated(object sender, DeactivatedEventArgs e)
{
    //Do something
}

3) Here You have a 4 useful events:

    // Code to execute when the application is launching (eg, from Start)
// This code will not execute when the application is reactivated
private void Application_Launching(object sender, LaunchingEventArgs e)
{
    //Do something
}

// Code to execute when the application is activated (brought to foreground)
// This code will not execute when the application is first launched
private void Application_Activated(object sender, ActivatedEventArgs e)
{
    //Do something
}

// Code to execute when the application is deactivated (sent to background)
// This code will not execute when the application is closing
private void Application_Deactivated(object sender, DeactivatedEventArgs e)
{
    //Do something
}

// Code to execute when the application is closing (eg, user hit Back)
// This code will not execute when the application is deactivated
private void Application_Closing(object sender, ClosingEventArgs e)
{
    //Do something
}

Here You can read more about handle this events: http://msdn.microsoft.com/en-us/library/hh821027.aspx