Can anybody here help me how I can solve it and also format it so it only write to xml file in this format dd/MM/yyyy
You can't and shouldn't - at least not without changing the schema. Your schema expressly specifies that it's an xs:date
- and the specified format of xs:date
is basically ISO-8601 (yyyy-MM-dd, with an optional offset from UTC), not dd/MM/yyyy.
I would strongly suggest that you store your data in the standardized representation - don't forget that a user should never have to see that; you can parse/format the date according to the user's culture, and then store it in ISO-8601 format. It's very important to differentiate between storage/communication formats and presentation formats.