LINQ to Entities
Most applications are currently written on top of relational databases. At some point, these applications will have to interact with the data represented in a relational form. Database schemas are not always ideal for building applications, and the conceptual models of applications differ from the logical models of databases. The Entity Data Model (EDM) is a conceptual data model that can be used to model the data of a particular domain so that applications can interact with data as entities or objects. For more information, see Entity Data Model.
Through the EDM, ADO.NET exposes entities as objects in the .NET environment. This makes the object layer an ideal target for Language-Integrated Query (LINQ) support. Therefore, LINQ to ADO.NET includes LINQ to Entities. LINQ to Entities enables developers to write queries against the database from the same language used to build the business logic. The following diagram shows the relationship between LINQ to Entities and the Entity Framework, ADO.NET 2.0, and the data source.