Question

I need show a simple dialog with the question : ‘Do you want to exit the application?’ YES or NO.
This dialog will be shown when the user presses the back button of the device.

I know how I can show this dialog , but I don’t know how to disable the back action: close app.

It’s always closed.

Answer 1

If I understand you correctly, you want to display a confirmation dialog when the user clicks the back button on the main page of your app to ask whether they really want to exit. If the user selects Yes the app exits, otherwise you cancel the back navigation. To do this, in the MainPage class constructor hook up an event handler

MainPage()
{
  BackKeyPress += OnBackKeyPressed;
}

void OnBackKeyPressed( object sender, CancelEventArgs e )
{
  var result = MessageBox.Show( "Do you want to exit?", "Attention!", 
                                MessageBoxButton.OKCancel );

  if( result == MessageBoxResult.OK ) {
    // Do not cancel navigation
    return;
  }
  e.Cancel = true;
}