private void edit_Click(object sender, RoutedEventArgs e) //user clicks to edit an assignment
        {
            MessageBox.Show("Save changes once they have been made.");

            if (viewAssignmentList.SelectedItems.Count == 0)
            {
                MessageBox.Show("No assignment selected.");
                return;
            }

            Assignment homework = (Assignment)viewAssignmentList.SelectedItems[0];

            MyAssignments.Remove(homework);
            viewAssignmentList.Items.Remove(homework);

            Classbox.Text    = homework.ClassName;
            Assigntitle.Text = homework.AssignName;
            notes.Text       = homework.Notes;

            string date  = homework.DueDate;
            string month = "";
            string year  = "";
            string day   = "";
            int    count = 0;

            foreach (char c in date)
            {
                if (count < 2)
                {
                    month += c;
                }
                if (count > 2 && count < 5)
                {
                    day += c;
                }
                if (count > 5)
                {
                    year += c;
                }
                count++;
            }

            monthbox.Text = month;
            daybox.Text   = day;
            yearbox.Text  = year;

            addassign.Content = "Save Changes";
        }
        private void complete_Click(object sender, RoutedEventArgs e) //user clicks to mark assignments as complete
        {
            if (viewAssignmentList.SelectedItems.Count == 0)
            {
                MessageBox.Show("No assignment selected.");
                return;
            }

            Assignment homework = (Assignment)viewAssignmentList.SelectedItems[0];

            MyAssignments.Remove(homework);
            viewAssignmentList.Items.Remove(homework);
            viewCompletedAssignments.Items.Add(homework);
            Completed.Add(homework);
            save_completed();
            save_to_file();
        }
        private void delete_Click(object sender, RoutedEventArgs e) //user clicks to delete an assignment
        {
            if (viewAssignmentList.SelectedItems.Count == 0)
            {
                MessageBox.Show("No assignment selected.");
                return;
            }

            Assignment homework = (Assignment)viewAssignmentList.SelectedItems[0];

            MessageBoxResult result = MessageBox.Show("Are you sure you want to delete " + homework.AssignName + " from you assignments?", "Important Message", MessageBoxButton.OKCancel);

            if (result == MessageBoxResult.Cancel)
            {
                return;
            }

            MyAssignments.Remove(homework);
            viewAssignmentList.Items.Remove(homework);
            save_to_file();
        }