Error Hanling RemainingChargePercentChanged Event - windows-phone-8

Question

I want to update a textblock whenever there is a change in battery percent. I found the event RemainingChargePercentChanged in the Windows.Phone.Devices.Power.Battery namespace. But whenever the eventhandler is called and i try to update the textblock, i struck with error.
the error is:
An exception of type System.UnauthorizedAccessException occurred in System.Windows.ni.dll but was not handled in user code.
Do I want to select any capabilities in AppManifest file??.. If so, what?
Any help will be appreciated.
Following is my code,
public partial class MainPage : PhoneApplicationPage
{
private readonly Battery _battery;
// Constructor
public MainPage()
{
InitializeComponent();
_battery = Battery.GetDefault();
_battery.RemainingChargePercentChanged += OnRemainingChargePercentChanged;
UpdateUI();
}
private void OnRemainingChargePercentChanged(object sender, object e)
{
UpdateUI();
}
private void UpdateUI()
{
sampletext.Text = string.Format("{0} %", _battery.RemainingChargePercent);
}
}

Answer 1

The problem is that the event handler is called on another thread, if you read the exception message it will say Invalid cross-thread access.
The solution is to change the Text property on the UI thread using the Dispatcher, like this:
Dispatcher.BeginInvoke(() => {
sampletext.Text = string.Format("{0} %", _battery.RemainingChargePercent);
});
Edit: or your whole UpdateUI function call:
private void OnRemainingChargePercentChanged(object sender, object e)
{
Dispatcher.BeginInvoke(() => {
UpdateUI();
});
}