Visual Studio 2017 xaml设计器不可用

Using Visual Studio Professional 2017 (Release 15.2 26430.16), when I open a xaml file for a desktop UI that I have developed, I can no longer see the xaml designer (I only see the raw xaml code). This is new behaviour and may be due to me having a system clean-out, so maybe I removed an SDK that I need or something like that?Using Visual Studio Professional 2017 (Release