Can I tell Visual Studio how treat a file with a custom file extension?

Can I tell Visual Studio how treat a file with a custom file extension? I want to be able to open a file with ".xxx" extension in Visual Studio and have CSS highlighting.

I've tried to do it by going to VS -> Tools -> Options -> Text Editor -> File E开发者_运维技巧xtension but in the Editor drop down there is nothing to specify "treat it as CSS".

In Visual Studio go to Tools > Options > Text Editor > File Extension

There you can add specific extensions and choose which 'Editor' Visual Studio uses for that extension.

There is a registry hack that you can use. http://www.engagesoftware.com/Blog/EntryId/117/Editing-SqlDataProvider-scripts-within-Visual-Studio.aspx

Basically, you look at HKLM:\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\9.0\Languages\File Extensions\.css (changing the version number based on your version of VS, and removing Wow6432Node if you aren't on a 64-bit OS) and make a copy of that, calling it .my-custom-extension

UPDATE According to a similar Stack Overflow question, for some extensions (i.e. CSS), there's another step to be taken. It says to take the GUID from the extension that you're copying, and find its entry in HKLM:\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\9.0\Editors and add a DWORD value in its Extensions key like the existing css value. That question also points to an extension in the VS gallery that does that. However, even after doing that, I'm still unable to get syntax highlighting, myself...

Tested on Visual Studio 2019. Tools > Options > Text Editor > File Extension add your file extension with '.' like .ejs (Node.JS View Engine) and then set it to one of known editors and press add: .ejs >> HTML Editor Close and reopen the files with .ejs in VS & you will see HTML markups on them.