Currently (I don't know why) ASP.NET Core assembly has been referenced by default, I don't think this should be the default behavior.
I'm sure that my My Extensions.linq file did not reference ASP.NET Core.
I'm guessing you've hit 'Set as default for new queries' at some point with those settings.
Change the settings to what you'd like for new for queries, and click the button again.
Thanks😊, that really solves my issue.
Can you take a look on my other function request here: https://forum.linqpad.net/discussion/2013/attribute-code-style-is-not-highlighted#latest