Problem by using Context.RewritePath when use persian language url in global.asax

i rewrite my url in global.asax by context.rewritepath.
i explain how do it work :when i click on menu Contactus my website goto this url: then in Application_BeginRequest i get the keywork (contactus) then i read the url rewrite for this key from database and after that i redirect the page to
Context.rewritepath(default.aspx?PID=contactus) every thing work correct when my PID is english language but when PID have Persian Language like this:Context.rewritepath(default.aspx?PID=?????? ??) it doesnt work correct and my master page show fine but not have detail of my page in master page ..
i think when use Context.rewritepath(PId by parsian language the format of text changed and my database cant find search for this key
at the end of my explain i tell you it work fine by persian language in local host but on server not work and thats my problem..
....please help me ???