Chapter 10

Data Access with the Entity Framework

What's in this chapter?

What is Object-Relational Mapping?

What is the Entity Framework?

How the Entity Framework works with databases

Using the Entity Framework to edit data

Wrox.com Code Downloads for this Chapter

The wrox.com code downloads for this chapter are found at www.wrox.com/remtitle.cgi?isbn=9781118314456 on the Download Code tab. The code discussed throughout this chapter is contained in the EFSimpleExample project.

In the past, Microsoft has been known to change the recommended data access strategy relatively frequently. For example, Data Access Objects (DAO) was released in the Visual Basic 3.0 time frame, followed by RDO (Remote Data Objects) as an option in the Visual Basic 4 days, and ADO (Active Database Objects) with Visual Basic 6. Of course, all of these were COM libraries, so it was no surprise when they were superseded by ADO.NET when the .NET Framework shipped. There have been remarkably few changes to ADO.NET since then.

The Entity Framework (EF) does not replace ADO.NET. You can continue to use ADO.NET without fear of it going away, even as a recommended data access tool. The Entity Framework simply provides a different — richer and more flexible — model for working with data sources.

Beyond simply being a set of classes you use to access your data, Entity Framework enables you to work naturally with the data using the classes you have designed, while saving the data to the underlying database schema. The Entity Framework provides the mapping necessary to convert the data structures, variable types, and relationships between the Visual Basic data you work with in your applications to the SQL Server, Oracle, or other database. It offers a means of working with your database more easily and more naturally than with ADO.NET, without requiring you to manually build your own data access layer.

Compared to LINQ to SQL, Entity Framework provides most of the same functionality for rapidly accessing your data. Where it differs is that Entity Framework provides a great deal of functionality not provided by LINQ to SQL, such as the ability to use databases other than SQL Server, and the ability to use client-side classes that don't directly map to database tables.