I\'m running a .Net 4.5 WPF application in Visual Studio 2015 Update 1 in a Debug build configuration.
In Tools > Options > Debugging > General I have checked Enable UI
Steps can be seen below, it works well for me.
Open VS, then type "Enable UI Debugging Tools for XAML" in the Quick Lanch box, enter to go to setting detail page (see screenshot below).
You can refer from Microsoft:
How to: Display WPF Trace Information - Visual Studio | Microsoft Docs