Programming Entity Framework: DbContext

Chapter 3. Adding, Changing, and Deleting Entities

In the previous chapter you saw how to get data from the database into memory. But this is only half the story. Most applications also need to make changes to that data and then push those changes back into the database. In this chapter we will take a look at how Entity Framework can be used to make changes to data. These changes fall into three main categories: adding new data, changing existing data and deleting existing data.

While looking at querying, we saw the main benefit of using an Object Relational Mapper (ORM), like Entity Framework, is that application code is written in terms of your object model. As you write your application, you don’t need to be looking at the shape of your tables and columns. Nor do you need to know how to write INSERT, UPDATE, and DELETE statements for your database. Entity Framework will take care of translating the operations you perform on your objects into SQL statements that will push these changes into the database.

As you perform operations on your object instances, Entity Framework uses its change tracker to keep track of what you have done. When you’re ready to commit the changes to the database, you call the SaveChanges method. SaveChanges will invoke the update pipeline, which is responsible for translating the changes to your object instances into SQL statements that are executed against your database. If you’ve developed applications using Entity Framework’s ObjectContext, you should ...