page.cs

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    base.OnNavigatedTo(e);

    InputPane.GetForCurrentView().Showing += OnKeyboardShowing;
    InputPane.GetForCurrentView().Hiding += OnKeyboardHiding;
}

protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
    base.OnNavigatingFrom(e);

    InputPane.GetForCurrentView().Showing -= OnKeyboardShowing;
    InputPane.GetForCurrentView().Hiding -= OnKeyboardHiding;
}

private void OnKeyboardShowing(InputPane sender, InputPaneVisibilityEventArgs args)
{
    MainPanel.Margin = new Thickness(0, 0, 0, args.OccludedRect.Height);
}

private void OnKeyboardHiding(InputPane sender, InputPaneVisibilityEventArgs args)
{
    MainPanel.Margin = new Thickness(0);
}