protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            this.Sample = e.Parameter as SampleDefinition;
            this.DataContext = this.Sample;
            var fe = (FrameworkElement)Activator.CreateInstance(this.Sample.SampleType);

            _placeHolder.Child = fe;

            base.OnNavigatedTo(e);
        }
        public void ShowSample(SampleDefinition sample)
        {
            this.SelectedSample = sample;

            sampleHistory.Add(sample);
            this.PageHeader = sample.Caption;

            RootFrame.Navigate(typeof(SamplePage), sample);

            OnPropertyChanged("BackButtonVisibility");
        }