筆記-C#設定DateTimePicker顯示空白

判斷資料庫內容是否為 "1990/1/1 上午 12:00:00"
if (myReader.GetString(21) == "" || myReader.GetString(21) == "1990/1/1 上午 12:00:00")
 {
      設定為空白
      UrlTimePicker.CustomFormat = " ";
      UrlTimePicker.Format = DateTimePickerFormat.Custom;
 }
 else
 {
      設為預設
      UrlTimePicker.Format = DateTimePickerFormat.Long;
      UrlTimePicker.Text = myReader.GetString(21);  
  }