DateTimePicker 如何返回日期！

1、如何使没有选择日期的DateTimePicker控件为空文本？（How to make the DateTimePicker show empty text if no date is selected?）

dateTimePicker1.CustomFormat = '';
dateTimePicker1.Format = DateTimePickerFormat.Custom;

2、如果选择日期的DateTimePicker控件返回当前日期

        private void dateTimePicker1_CloseUp(object sender, EventArgs e)
        {
            this.dateTimePicker1.Format = DateTimePickerFormat.Long;
        }
或者
       private void dateTimePicker1_CloseUp(object sender, EventArgs e)
        {
               dateTimePicker1.CustomFormat = "ddd dd MMM yyyy";;
        }