Entity Framework (EF)

Entity Framework (EF) is an object-relational mapper that enables .NET developers to work with relational data using domain-specific objects. It eliminates the need for most of the data-access code that developers usually need to write.

Entity Framework is actively developed by the Entity Framework team which is assigned to the Microsoft Open Tech Hub and in collaboration with a community of open source developers. Together we are dedicated to creating the best possible data access experience for .NET developers.

Entity Framework (EF) is an open source object-relational mapping (ORM) framework for ADO.NET, part of .NET Framework. 

The Entity Framework is a set of technologies in ADO.NET that support the development of data-oriented software applications. Architects and developers of data-oriented applications have struggled with the need to achieve two very different objectives. They must model the entities, relationships, and logic of the business problems they are solving, and they must also work with the data engines used to store and retrieve the data. The data may span multiple storage systems, each with its own protocols; even applications that work with a single storage system must balance the requirements of the storage system against the requirements of writing efficient and maintainable application code.

The Entity Framework enables developers to work with data in the form of domain-specific objects and properties, such as customers and customer addresses, without having to concern themselves with the underlying database tables and columns where this data is stored. With the Entity Framework, developers can work at a higher level of abstraction when they deal with data, and can create and maintain data-oriented applications with less code than in traditional applications. Because the Entity Framework is a component of the .NET Framework, Entity Framework applications can run on any computer on which the .NET Framework starting with version 3.5 SP1 is installed.

Entitiy Framework Architecture

The architecture of the ADO.NET Entity Framework, from the bottom up, consists of the following:

• Data source specific providers, which abstract the ADO.NET interfaces to connect to the database when programming against the conceptual schema.

• Map provider, a database-specific provider that translates the Entity SQL command tree into a query in the native SQL flavor of the database. It includes the Store-specific bridge, which is the component responsible for translating the generic command tree into a store-specific command tree.

• EDM parser and view mapping, which takes the SDL specification of the data model and how it maps onto the underlying relational model and enables programming against the conceptual model. From the relational schema, it creates views of the data corresponding to the conceptual model. It aggregates information from multiple tables in order to aggregate them into an entity, and splits an update to an entity into multiple updates to whichever table(s) contributed to that entity.

• Query and update pipeline, processes queries, filters and updates requests to convert them into canonical command trees which are then converted into store-specific queries by the map provider.

• Metadata services, which handle all metadata related to entities, relationships and mappings.

• Transactions, to integrate with transactional capabilities of the underlying store. If the underlying store does not support transactions, support for it needs to be implemented at this layer.

• Conceptual layer API, the runtime that exposes the programming model for coding against the conceptual schema. It follows the ADO.NET pattern of using Connection objects to refer to the map provider, using Command objects to send the query, and returning EntityResultSets or EntitySets containing the result.

• Disconnected components, which locally cache datasets and entity sets for using the ADO.NET Entity Framework in an occasionally connected environment.

• Embedded database: ADO.NET Entity Framework includes a lightweight embedded database for client-side caching and querying of relational data.

• Design tools, such as Mapping Designer, are also included with ADO.NET Entity Framework, which simplifies the job of mapping a conceptual schema to the relational schema and specifying which properties of an entity type correspond to which table in the database.

• Programming layer, which exposes the EDM as programming constructs which can be consumed by programming languages.

• Object services, automatically generate code for CLR classes that expose the same properties as an entity, thus enabling instantiation of entities as .NET objects.

• Web services, which expose entities as web services.

• High-level services, such as reporting services which work on entities rather than relational data.