White Screen After the Splash and before the MainAcitvity

I have Created a new project in Xamarin.forms I have Added the splash Screen and main activity.On the Code Behind when i set page like
MainPage=new MainPage(); Then its working fine.
when i use MainPage= new Navigation(new MainPage()); then its produce white screen after splash how to handle this problem. i didnot find any working
Salution,