#1,038 – Another Way to Prevent Certain Dates from Being Selected

You can limit the dates available for selection in a Calendar or DatePicker control in a few different ways.

• Specify blackout dates
• Specify allowed start and end dates
• Handle the SelectedDateChanged event

If you want to prohibit some combination of dates, but have to do some calculation to figure out which dates should be prohibited, you can add a handler for the SelectedDateChanged event.

        <Label Content="Pick a day to go skydiving:"
               Margin="5"/>
        <DatePicker Margin="5,0,5,5"
                    SelectedDateChanged="DatePicker_SelectedDateChanged" />

In the handler, if the selected date is not one that you allow, you can undo the fact that it was selected.

        private void DatePicker_SelectedDateChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
        {
            if (e.AddedItems.Count > 0)
            {
                DateTime dayToDive = (DateTime)e.AddedItems[0];
                if ((dayToDive.DayOfWeek == DayOfWeek.Friday) &&
                    (dayToDive.Day == 13))
                {
                    MessageBox.Show("Dude, that's really an unlucky day to go skydiving.");
                    ((DatePicker)sender).SelectedDate = null;
                }
            }
        }

If we pick a Friday the 13th, the application warns us and then unselects the date.