I am trying to make an application that can add dates for hotel rooms and get the average time between the dates. I have made 2 calendars, 1 for the starting date and the other one for the ending date. When I show the output in the listbox, I don't know how to get the days between this dates. I need them to calculate the average.

I've tried to get the dates but I'm confused with the datetime things.

```
lbDates.Items.Add(string.Format("{0}, {1}, {2}, {3}", cmbBoxRoom.SelectedItem, tbBooking.Text, calArrival.SelectedDate, calDeparture.SelectedDate));

```

How can I get the between of the dates so I can calculate with that?