Animation when changing MainPage of the application

I am using a MasterDetail template and I also have a login page. In my app when I am logged out I have set:

MainPage = new LoginPage();

When I will successfully log in I am just changing MainPage to MasterDetailNavigation like this:

MainPage = new MasterDetailNavigation();

However, there is no animation (page transition) when I am changing MainPage. How can I add it? It would be great to have i.e. the same animation which is when we are doing:

Navigation.PushAsync(new SomePage())

How can I achieve this animation?