What is the ADO.NET Entity Framework?

The ADO.NET Entity Framework is an extended ORM technology from Microsoft. We say it is an extended ORM because it has many additional features compared to a typical ORM. ORMs often use metadata and factory classes to retrieve data or collections of data.

On the contrary, using Entity Framework, you can easily map your data to be accessible in a relational representation in the database to objects, no matter how the mapping is implemented. You can expose different data views to your application without having to change your relational schema. In essence, this allows the applications to have their own view of the data. The applications can even reuse the same views of data among themselves.

The major difference between Entity Framework and ORM tools is the EDM and the former's ability to query data using strongly typed LINQ. You can even use Entity SQL, a T-SQL-like query language to query the EDM, to execute dynamic queries. In addition to what a typical ORM framework provides, the Entity Framework provides and supports entity inheritance, entity composition, and a flexible, loosely-coupled, three-tiered model consisting of the conceptual model, the mapping layer, and the storage model. Please refer to the Appendix section for links to resources on this topic.

Entity Framework even enables you to extend the existing schema. In other words, you can extend the generated entity classes to create your own custom entity classes. You can define relationships of any kind such as one-to-one, one-to-many, and even many-to-many.