private async void PeroidsGridView_ItemClick(object sender, ItemClickEventArgs e)
 {
     GridView        gridView = sender as GridView;
     Peroid          p        = (Peroid)e.ClickedItem;
     GradeInfoDialog dialog   = new GradeInfoDialog(p);
     await dialog.ShowAsync();
 }
 public GradeInfoDialog(Peroid peroid)
 {
     this.InitializeComponent();
     Time.Text    = peroid.Time;
     Percent.Text = peroid.Percent;
     Letter.Text  = peroid.LetterGrade;
     Eval.Text    = peroid.Eval;
     try {
         if (peroid.Comment == null)
         {
         }
         Comment.Text = peroid.Comment;
     } catch (System.NullReferenceException) {
         Comment.Text = "N/A";
     }
 }