Entity Framework Core Cookbook - Second Edition

Getting entities from the local cache

When using an Object-Relational Mapper (ORM) such as Entity Framework, a very important feature to keep in mind is this: when an entity is materialized as the result of executing a query, it is stored in an in-memory cache. This is usually referred to as First Level Cache, but Martin Fowler gave it another name: Identity Map. In its definition, he said that the purpose of this pattern is to ensure that each object gets loaded only once, by keeping every loaded object in a map. If you think of it, it is a good thing performance-wise, because there's always a cost in instantiating classes and hydrating them from the records obtained from the data source. This is used internally by ORMs, but we can also make ...