How to deal with high performance EF Core operation
By default, EF Core tracks changes to entities, and then sends updates to the database when one of the SaveChanges methods is called. Changes are only sent for properties and relationships that have actually changed. Also, the tracked entities remain in sync with the changes sent to the database. This mechanism is an efficient and convenient way to send general-purpose inserts, updates, and deletes to the database. These changes are also batched to reduce the number of database round-trips.
However, it is sometimes useful to execute update or delete commands on the database without involving the change tracker. EF7 enables this with the new ExecuteUpdate and ExecuteDelete methods. These methods are applied to a LINQ query and will update or delete entities in the database based on the results of that query. Many entities can be updated with a single command and the entities are not loaded into memory, which means this can result in more efficient updates and deletes.
However, keep in mind that:
The specific changes to make must be specified explicitly; they are not automatically detected by EF Core. Any tracked entities will not be kept in sync. Additional commands may need to be sent in the correct order so as not to violate database constraints. For example deleting dependents before a principal can be deleted. All of this means that the ExecuteUpdate and ExecuteDelete methods complement, rather than replace, the existing SaveChanges mechanism.
What I have done and tried to show you is a simple piece of code as an example.