In Visual Studio 2013 I started getting the following error when trying to open C# files:
No EditorOptionDefinition export found for the given option name: T
I had a same problem I did small change for Jake Answer
1 Close Visual Studio 2 Search ComponentModelCache Folder 3 Rename folder 4 Restart the visual Studio
And it start to work
It happened to me again then this time I tried Web Essentials 2013.5 then Its start to work. Hope this will help you.