C# UWP Reflection Get All Classes that extends specified class

I'm currently developing an APP using UWP in C#. I wanted to use reflection in order to discover available classes and dynamically let users select which one to use. It seems that UWP Reflection doesn't work exactly the same way as for other C# applications. So I can't find code that work. I need to discover which classes are available that extend a particular class.

Can someone point me on the right direction?