private void AnalizeButton_Click(object sender, RoutedEventArgs e) { if (Start != null && End != null) { var counter = new List <List <int> >(); var tmpDate = Start.SelectedDate; while (tmpDate <= End.SelectedDate) { var countList = new List <int>(); var tmpHour = tmpDate.Value; while (tmpHour.Hour <= 23) { countList.Add(pm.GetNumberOfSessionsByTime(tmpHour, tmpHour.AddMinutes(59).AddSeconds(59))); tmpHour.AddHours(1); } counter.Add(countList); tmpHour.AddDays(1); } foreach (var c in counter) { var dataColumn = new DataGridTextColumn(); } } else { MessageBox.Show("Please enter both dates"); } }