The Bug
In preparation for writing a blog post on my use of T4 templates to generate boilerplate web page data maintenance screens, I came across the following error whenever I used certain keys in the file (including the backspace, return and cursor keys):
Could not load type Micorsoft.VisualStudio.Package.Variant from assembly
Microsoft.VisualStudio.Package.LanguageService.15.0, Version=16.0.0.0, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a
Debugging the Bug
I initially tried updating and then re-installing Visual Studio to try and fix with no success. I was then able to isolate the issue to an extension that I use for syntax colouring and Intellisense in T4 files, the highly recommended Devart T4 Editor. By removing the extension, I could move around the T4 file with the cursor keys without an error - but also without the stylings of the Devart.
Next step was to downgrade Visual Studio to an earlier version, easily accessible here.
Going back one minor update version (16.10.1) made no difference, but a full update version lower (16.9.8) did the trick!
Will Devart provide a fix for this wonderful (free) tool?