How to make a custom Frame

So, I'm working on an app to show information about city locations and I wanted to use something similar to the Frame that is possible in Xamarin.

I was looking for something like this is attached

But I have not found any documentation on how to extend the Frame class, I tried creating a public class and inheriting from Frame but to no avail.

And I want to do this programatically (In C#, not xaml)