Basic Date Picker : AutoPostBack
If a new date is selected, the SelectionChangedEvent (AutoPostBack)
will fire. In this sample an IsNull check is made on the PostBack
to to determine whether a valid date was supplied. If a valid date
was supplied, the SelectedDateFormatted property is written to a label
Similar to the ASP.NET TextBox Control, the AutoPostBack property must be set to
The SelectionChanged Event will fire when the value in the TextBox changes
either by selecting a date in the calendar or editing the value manually.