At Build 2018 we announced that we are enabling Windows desktop applications (Windows Forms and Windows Presentation Framework (WPF)) with .NET Core 3.0. You will be able to run new and existing Windows desktop applications on .NET Core and enjoy all the benefits that .NET Core has to offer, such as application-local deployment and improved performance.
We want to make sure that .NET Core 3.0 includes all the APIs that your applications depend on. So, in order to learn about which APIs are being used, we are releasing Portability Analyzer that will report the set of APIs referenced in your apps that are not yet available in NET Core 3.0. This API list will be sent to Microsoft and will help us prioritize which APIs we should incorporate to the product before it ships.