What Is C# Entity Framework? A Comprehensive Guide

What Is C# Entity Framework?

Entity Framework (EF) is an object-relational mapper for .NET developers that allows them to work with relational data using domain-specific objects. It eliminates the majority of the data-access code that developers must routinely write.

Developers may work with data in domain-specific objects and properties, such as customers and customer addresses, without worrying about the underlying database tables and columns where this data is kept, courtesy of the Entity Framework.

What Is the Use of Entity Framework in C#?

Developers can work with data in domain-specific objects and properties, such as customers and customer addresses, without worrying about the underlying database tables and columns where this data is kept, courtesy of the Entity Framework.

Entity Framework is used in the following scenarios.

• Create an MVC web app.
• Set up the site style.
• Install Entity Framework 6.
• Create the data model.
• Create the database context.
• Initialize DB with test data.
• Set up EF 6 to use LocalDB.
• Create controller and views

Features of C# Entity Framework 

• Entity Framework is a lightweight and extensible object-relational mapping (ORM) technology. According to the individual needs of each project, developers can add or delete specific components from the ORM system.
• Entity Framework supports multiple platforms like Windows, Linux, and macOS.
• Entity Framework supports both relational and non-relational data sources.  Entity Framework works efficiently with widely used databases like SQL Server, SQL Server Compact, SQLite, PostgreSQL, Azure Table Storage, and IBM Data Server.
• Entity Framework makes it easier for programmers to perform create, read, update and delete (CRUD) operations by supporting databases. It also makes it easier for developers to perform unit testing by keeping in-memory tables.
• C# Entity Framework allows us to configure the Entity Framework model through data annotation properties or the Fluent API, to alter default conventions.
• C# Entity Framework provides a series of migration commands that can be run from the NuGet Package Manager Console or the Command Line Interface. To create or manage underlying database Schema

Entity Framework Development Approaches

There are mainly three approaches to create entity frameworks:

1. Code First Approach

This approach first targets a database that does not exist and then creates it. It allows the developers to define and make new models with C# and .NET classes. In this approach, you can use empty databases and add tables too.

2. Model First Approach

This model is best suitable for new projects where the database does not exist. This model is stored using the EDMX file and can be viewed and edited by the developer.

3. Database First Approach

This approach is an alternative for the code-first approach and the model-first approach. It creates the model and codes from the database in the project and connects them with the database and developer. 

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Basic Workflow in Entity Framework

1. First, you need to define the model. Defining the model consists of domain classes, context classes derived from DbContext, and configuration.
2. To insert data, you need to add a domain object for a context and call the savechanges() method. You need to use the insert command and execute it to the database.
3. For reading data, executing the LINQ-to-Entities query in your preferred language like C# or .NET will be useful. EF API will convert the query to the SQL query, which will be provided to the database for execution. 
4. For editing, updating, deleting, and removing entities objects, you should call the savechanges() method. EF API will build and execute the commands in the database.

Entity Framework Architecture

The Architecture of Entity Framework consists of the following components:

• The Entity Data Model
• LINQ to Entities
• Entity SQL
• The Object Services Layer
• Entity Client Data provider
• ADO.Net Data Provider

The Entity Data Model

The entity data model (EDM) is made up of three parts:

Conceptual Model: The conceptual model represents the model classes (also known as entities) and their relationships. This will be independent of the database table's architecture. It describes your business objects and their relationships in XML files.

Mapping Model: A mapping model specifies how the conceptual model is translated into a storage model. The Mapping model maps the conceptual and logical layers (storage layer). It integrates the business objects and relationships in the abstract layer with the tables and relationships in the logical layer.

Storage Model: The storage model represents the schema of the underlying database. The database design model contains tables, views, keys, stored procedures, and their relationships.

LINQ to Entities

Queries against the object model are written using the LINQ-to-Entities (L2E) query language. The entities defined in the conceptual model are returned.

Entity SQL

Internally, these E-SQL queries are converted to SQL queries that are data store dependent. E-SQL queries are converted to datastore-specific query languages like T-SQL via the Entity Framework (Transact SQL).

The Object Services Layer

The Object Services layer includes the Object Context, representing the interaction session between the applications and the data source. The fundamental purpose of the Object Context is to conduct various operations, such as adding and deleting instances of things and querying the database to save the modified state.

Entity Client Data provider

The Object Services layer includes the Object Context, representing the interaction session between the applications and the data source. The fundamental purpose of the Object Context is to conduct various operations, such as adding and deleting instances of things and querying the database to save the modified state.

ADO.Net Data Provider

These source-specific providers abstract the ADO.NET interfaces used to connect to the database while programming against the conceptual schema. It uses a command tree to translate standard SQL languages like LINQ into native SQL expressions, which it then executes on the given DBMS system.

Installation of EF

• From the Tools menu, choose NuGet Package Manager, and then select choose Package Manager Console.
• Enter the following command in the Package Manager Console window:

Install-Package EntityFramework

Context Class in Entity Framework

It is the most crucial class when it comes to working with EF 6 or EF Core. It helps execute the create, read, update, and delete commands in a database schema. It is a derived class in the Entity Framework. It is also used to configure domain classes, map databases, track changes, and store cache.

What Is an Entity in Entity Framework?

An entity is a class in an Entity Framework that maps the database tables. 

EF API can map each entity to tables and each property of an entity to a column in the database.

Entities mainly consist of two types in an entity framework:

1. Scalar Property

Scalar properties are those properties that are primitive. It maps a column in a database table that stores the data. E.g., student id, student name, class are the scalar property of a student entity.

2. Navigation Property

This property is responsible for the relationship of one entity to another. There are two types of navigation properties:

i) Reference Navigation Property

When an entity has the property of another type of entity property, it is called reference navigation property. It points to a single entity but represents the multiplicity of one.

ii) Collective Navigation Property

When an entity has the property of generic collection type, it is known as collective navigation property. It has the multiplicity of many.

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Types of Entities in Entity Framework

There are two types of entities in an entity framework:

1. POCO Entities (Plain Old CLR Objects)

It is an entity class that does not depend on any framework-specific base class. It is the normal .NET CLR class that's why it is named "Plain Old CLR Objects". It supports many operations like update, create, and delete that are generated by the entity data model.

2. Dynamic Proxy Entities (POCO Proxy)

Dynamic proxy entities are runtime classes and wrap up the POCO entity. These entities are lazy loading classes. It is only supported by EF 6; EF Core 2.0 does not support it yet.

Entity States

EF API is responsible for maintaining the states of entities throughout their lifecycle. Each entity possesses a state according to the operation performed by the context class. The entity state can be represented by an enum System.Data.Entity.EntityState in EF 6.

Persistence in Entity Framework

There are two types of persistence scenarios in the entity framework:

1. Connected Scenarios

In this scenario, the same context class is used to retrieve and save entities. It keeps track of all databases during the whole lifecycle. It is useful for the databases for the same network.

2. Disconnected Scenarios

In this scenario, a different context is used to retrieve and save data. One instance of context class is used to retrieve the data, and another is used to save the data.

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Conclusion

This tutorial on ‘ASP.NET Entity Framework’ covers its features and architecture. Apart from what ASP.NET Entity framework is, it also includes why to use it and its version history. Proceeding further, you will see the comparison between EF6 and EF Core. 

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