Fix orientation for whole app in ios

I am developing application in PCL project.

In that I change only one page to Landscape. I am able to do that using 2nd Answer in this link.

Also I need to be my app in portrait mode except this one page. But problem is it works only when my phone's auto rotate is off. If my phone's rotation is on and if I open my app in landscape, then my app also opens in landscape.

I tried to return Portrait from GetSupportedInterfaceOrientations function in AppDelegate.cs. but then it won't let me rotate that single page to landscape. It remains portrait.

And If I write condition like 'return landscape if current page is this and return portrait for all others', it doesn't work. I dont know why, it returns correct orientation but my page is not rotated.

Any help would be appreciated !
Thank you