Thank you for reply. If your system langauge in the Control Panel (Regional Setting >Advance) is Farsi then it should accept the RightToLetf property. If your system langauge is not Farsi then RightToLeft property will be ignored.
Please set the default langauge Farsi in Advance Tab of Reginal Setting and then try the righttoleft.
Congratulation for Ramadan
Zaheer