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12: Customizing Entity Framework Objects. The recipes in this chapter show you how to respond to key events, such as when objects are persisted. We also show how to customize the way those events are handled. 13: Improving Performance. For many applications, getting the best performance possible is an important goal. This chapter shows you several ways to improve the performance of your Entity Framework applications. 14: Concurrency. Lots of instances of your application are changing the database. How do you control who wins The recipes in this chapter show you how to manage concurrency. 15: Advanced Modeling. This is the last of three chapters that focuses on modeling. The recipes in this chapter show you how to solve some of the most vexing modeling problems you are ever likely to encounter.

At present there are four perspectives on model development in Entity Framework. Each of these perspectives is at a different level of maturity in the product and at a different level of use in the community. The initial perspective supported by Entity Framework is called Database First. Using Database First, a developer starts with an existing database that is used to create an initial conceptual model. This initial model serves as the starting point for further development. As changes occur in the database, the model can be updated from these database changes. Database First was the initial perspective supported in Entity Framework, is the best-supported approach, and is widely used to migrate existing applications to Entity Framework. The current release of Entity Framework introduced the Model First perspective. With Model First, the developer starts with a blank design surface and creates a conceptual model. Once the conceptual model is complete, Entity Framework can automatically generate a script to create a complete database for the conceptual model. In this release there is limited support for many of the modeling scenarios. As you might expect, realizing an arbitrarily complex conceptual model in a traditional relational database is an enormous challenge. The support for this perspective will mature over time and will likely become the dominant approach, particularly for new projects. Persistence ignorance, which is supported in many ORM products, is now supported in the current version of Entity Framework. With persistence ignorance, you can use plain old CLR objects, usually referred to as POCO, as entity types. There is no need for them to inherit from EntityObject. We have devoted a number of recipes to POCO. Finally, an emerging perspective is Code First. In this approach, there is no .edmx file (which encapsulates model and mapping information). Your objects create and use a model dynamically at runtime. This perspective is still in the experimental stage and is available as a Community Technology Preview. In this book, we focus on the Database First perspective. This perspective is the most widely used and most mature approach. Many, if not most, developers in the Entity Framework community find themselves working with existing applications or developing models that are not readily supported by the other perspectives. We also have to share a dirty little secret: many existing applications don t exactly use the best database designs. Way too often we find ourselves working with databases (of course, created by other less talented developers) that are poorly designed. As developers, sometimes in larger organizations with lots of process control, or with lots of fragile legacy code, we can t change the database enough to really fix the design. In these cases, we simply have to work with the database design we have.

Many of the recipes we selected for this book take on the task of modeling some of these more challenged database designs. We ve found hundreds of examples of these databases in the wild and we ve worked with many developers in the Entity Framework community who have struggled to model these databases. We ve taken these experiences and selected a number of recipes that will help you solve these problems.