DbContext & DbSet

DbContext is the heart of every EF Core application. It's the object you instantiate, the object you query through, and the object you call SaveChanges on. Under the hood it plays three roles at once: a Unit of Work that batches your changes into one transaction, an Identity Map that keeps a single in-memory copy of each row you've touched, and a change tracker that figures out which entities are new, modified, or deleted. This lesson covers how to define a DbContext, configure its connection, register it with dependency injection, manage its lifetime, and call SaveChanges to push your changes to the database.