C#

namespace WpfApplication2
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            DateTime current = DateTime.Now;
            Entrance();
        }

        private void Entrance()
        {
            selectedDate.Text = DateTime.Now.ToString("MM/dd/yyyy");
        }

        private void displayEvents_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                DateTime selected = DateTime.Parse(enteredDate.Text);
                selectedDate.Text = selected.ToString("MM/dd/yyyy");
            }
            catch (FormatException)
            {
                MessageBox.Show("The date you enterd was invalid.\n\nPlease reenter the date in
 the format MM/dd/yyyy.");
            }
        }

        private void saveNewEvent_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                WriteToFile();
                WriteToEventList();
            }
            catch (FormatException)
            {
                MessageBox.Show("The date you enterd was invalid.\n\nPlease reenter the date in the format MM/dd/yyyy.");
            }
        }

        private void WriteToFile()
        {
            DateTime newEntry = DateTime.Parse(newDate.Text);
            string addEvent = "";
            addEvent = newEvent.Text;
            using (TextWriter writeEvent = new StreamWriter("datebook.txt"))
            {
                writeEvent.WriteLine(newEntry.ToString());
                writeEvent.WriteLine(addEvent); 
            }
        }

        private void WriteToEventList()
        {
            DateTime newEntry = DateTime.Parse(newDate.Text);
            string addEvent = "";
            addEvent = newEvent.Text;
            eventsList.AppendText(String.Format("{0}\t{1}\n", newEntry, addEvent));
        }
    }
}