Exception Message:
PM> Remove-Migration
The migration 'AddingEFExtensions' has already been applied to the database. Revert it and try again.
Cause:
This error arises when attempting to remove a migration that has already been committed to the database.
Solution:
Before using Remove Migration, make sure to revert the database to the state prior to the migration you intend to remove. This can typically be achieved using the Update-Database command followed by the name of the migration preceding the one you wish to remove.