There is no way to query PackageReferences in a project

There are API's to Add or Remove a PackageReference, but there is currently no way to ask if a package reference exists in a project, and if so, what version is it. There's also no way to just enumerate all existing package references.

So you can't positively know if a package is referenced in a project until you have **successfully** restored packages in a project, at which time existing NuGet related package services will have *installed* version information and let you enumerate *installed* packages.