Category: 2 Minute Tutorial

Many of the applications I’ve been looking at developing during my Windows Phone 7 endeavours have a common requirement – the ability to check if this is the first run of the application. For example, if you are designing an application that will access a service like Twitter or Facebook, you’ll need to gather the users login details in order for your application to function.

For example, on the first run of the application, we’ll want to display a login dialog, gather the users information and store it. We can use the isolated storage facility on Windows Phone 7 devices to store this information. If you’re unfamiliar with isolated storage, check out my previous post here.

Step 1 – Store a value to track if this is the first run

I added this code to the ‘Application_Launching’ function. This function is called each time your application is launched.


// 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)
{
// Set if this is the first run of the application or not
if (!settings.Contains("firstRun"))
{
settings.Add("firstRun", (bool)true);
}
else
{
settings["firstRun"] = (bool)false;
}
}


Step 2 – Intercept navigation to your main page, redirect if necessery

Next, we need to create an event handler to intercept any navigation the your main page, and redirect to your ‘first run’ page (login or whatever) if necessery.

First we check if we’re navigating to our main page, if we’re not the function just returns and navigation proceeds as normal. If we are, we’ll ensure that if it’s the first run of the application, the user will be redirected to a login page etc.


///

/// Event handler to intercept MainPage navigation
///

/// the frame /// navigation args void RootFrame_Navigating(object sender, NavigatingCancelEventArgs e)
{
// Only care about MainPage
if (e.Uri.ToString().Contains("/MainPage.xaml") != true)
{
return;
}

// Check if this is the first run of the application
if ((bool)settings["firstRun"])
{
e.Cancel = true;
RootFrame.Dispatcher.BeginInvoke(delegate
{
RootFrame.Navigate(new Uri("/FirstRun.xaml", UriKind.Relative));
settings["firstRun"] = (bool)false;
});
}
else
{
RootFrame.Dispatcher.BeginInvoke(delegate
{
RootFrame.Navigate(new Uri("/MainPage.xaml", UriKind.Relative));
});
}
}


Step 3 – Ensure the event handler is called when navigation occurs

Finally, we need ensure that the event handler we created in step 2 above is actually called when any navigation occurs. To accomplish this, all we need to do is add the following code in the constructor of the ‘App.xaml.cs’ file:

// Add this code to the constructor in App.xaml.cs

// Route the user to the login screen if it's the first run of the application
RootFrame.Navigating += new NavigatingCancelEventHandler(RootFrame_Navigating);

That’s pretty much it, I’ve successfully used the above mechanism in two different applications, hope this saves you some time!