I just wanted to share a fresh experience.
If you have IFrame based Facebook application, previously it was too difficult to use FBML tags. But a few days ago, after last API revisions, fb added new functionality which helps developers in useing bıth FBML and IFrame in same application.
For example, my application was in IFrame format. But I needed to use fb:request-form . With the help of this new functionality, I was able to use CanvasFBMLBasePage as base class in my invite page code behind. And in the design view used fbml code below. And
finally set the invitation link as invite.aspx?fbforcemode=fbml . Thats All !
But do not forget! If you use FBML, your application must be reached by facebook. I mean you can not use localhost or any other place where fb can not access. You must publish your app on web.
Of course the vice versa is also applicable. If you use FBML app, you can use IFrame pages by just using fbforcemode=iframe query string GET parameter.
I hope it helps some one