Windows Phone 7 project not updating properly

Question

Using VS2015 I upgraded a WP 7.1/7.7 project.
I was developing and testing fine using the 8.1 emulator for a couple of months until I realized that I was missing then newer 8.1 controls in the toolbox.
I started a new separate 8.1 project and I can see a large range of new controls like Listbox and ComboBox that don't exist in the 7.1 upgraded app.
Looking at the project properties the Target Windows Phone OS Version is set to Windows Phone 8.1.
I've searched all over and can't find any other settings to tweak. The project has the older Windows Phone Toolkit 4.2013.8.16.

I wonder if that blocks the new tools?
How can I get the 8.1 one controls to turn on?

Answer 1

There's two frameworks on Windows Phone 8.1: Silverlight and WinRT. When you upgraded to 8.1, since your project was using Silverlight (WinRT wasn't available on Windows Phone 7), it was set to target Silverlight 8.1. That's why you can't use the WinRT controls. The thing is, WinRT and Silverlight have completely different controls, so you can't automatically convert a project from one to another. You've got to consider whether you really need/want to use WinRT. If so, you'll have to rewrite large portions of your UI code to accommodate with the new controls.

If you want to make the conversion, you should first have a look at the Microsoft documentation to understand the key differences between the two frameworks: https://msdn.microsoft.com/en-us/library/windows/apps/hh452743.aspx

Note that Windows 10 universal apps (the ones that can run on phone and desktop) use WinRT. Silverlight is deprecated, and sooner or later you'll have to upgrade.