See the question and my original answer on StackOverflow

UWP apps (or Windows Store apps, or apps in what's called sometimes the "AppX application model") information can be queried from official APIs.

These APIs don't have a C# equivalent AFAIK but I've provided sample code to do this in my answer to a similar question here on SO: Getting icon of “modern” Windows app from a desktop application?

The sample application dumps all current loaded Windows Store packages & apps.

Note there is not just one icon for a UWP app, there may be many, to be able to adapt to a specific device, form factors, etc. The sample code has a utility that gets the highest scale image for a given resource.