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An important class, DbEntityEntry helps you retrieve a variety of information about an ENTITY. DbContext offers the Entry method for retrieving an instance of DBEntityEntry of a specific entity. 

Example: 

You can access the entity STATE, as well as the current and original values of all properties of an entity using the DbEntityEntry. EntityState can be set using the DbEntityEntry, as shown below.  

With .NET Framework 3.5, Microsoft introduced Entity Framework in 2008. Since then, the company has RELEASED a number of Entity Framework versions. EF 6 and EF Core are the two latest versions of Entity Framework. With Entity Framework, .NET developers can work with a database using .NET objects. By doing this, the traditional method of accessing data through code is eliminated. Basically, it allows you to read and write data from a database. We have compiled a list of the top Entity Framework INTERVIEW questions to assist freshers and experienced developers who are seeking new career opportunities and skills that require Entity Framework knowledge and skills. 

In Entity Framework, EDM refers to the 'Entity Data Model'. It is CONSIDERED as an entity-relationship prototype that assigns some basic prototypes for the data using VARIOUS modeling procedures. Moreover, it is defined as a SET of principles pertaining to the formation of data, regardless of how it is collected. Shortly, it's just a SIMPLE link or CONNECTION created between the database and the prototype. The steps for creating an Entity Data Model are as follows:   

• Right-click on a project in the Solution Explorer.
• Select the Add>New Item option from the menu.
• Select the ADO.Net Entity Data Model arrangement or template.
• Please enter a name and click the 'Add' button.

NET Data Provider for SQL SERVER is INCLUDED in .NET CODE by using the namespace System.Data.SqlClient. 

ObjectSet is generally CONSIDERED as a specific type of data set that is commonly USED to READ, UPDATE, create, and remove operations from existing entities. Only the ObjectContext instance can be used to create it. No Entity SQL method is supported by it. 

The injection-proof NATURE of Entity Framework lies in the FACT that it generates PARAMETERIZED SQL commands that help prevent our database from SQL injections.  

By inserting some malicious INPUTS into queries and parameter names, one can generate a SQL injection attack in Entity SQL syntax. It is best to never COMBINE user inputs with Entity SQL commands text to prevent or avoid this problem.

SQL INJECTION is a method that hackers use to access sensitive INFORMATION from an organization's DATABASE. This application-layer attack is the result of INAPPROPRIATE coding in our applications, allowing hackers to inject SQL statements into your SQL CODE.   

The most common cause of SQL Injection is that user input fields allow SQL statements to pass through and directly query the database. ADO.NET Data Services queries are commonly affected by SQL Injection issues. 

There are TWO types of Data Access Architecture supported by the ADO.NET Framework: 

• Disconnected data access: Disconnected data access is POSSIBLE with the Data ADAPTER object. Datasets work independently of databases, and the data can be edited.
• Connected data access: A Data Reader object of a Data Provider allows you to access linked data. Data can be accessed quickly, but EDITING is not PERMITTED.

Rather than CREATING database schemas, MODIFYING database schemas, tracking changes, etc., MICRO ORMs focus on working with database TABLES. EF 6.x and EF Core PROVIDE a full set of capabilities and features, making them ORMs. 

Complex TYPES are defined as the non-SCALAR properties of entity types that assist in organizing scalar properties WITHIN entities. In ADDITION to scalar properties, complex types may also have other complex type properties. Instances of complex types are complex OBJECTS. 

In Entity Framework, inheritance is primarily divided into three types: 

• Table per Hierarchy (TPH): The TPH inheritance representation shows one table per inheritance hierarchy class. A discriminator column also aids in DISTINGUISHING between inheritance classes. This is Entity Framework's default inheritance mapping technique.
• Table per TYPE (TPT): In this inheritance method, each domain class has its own table.
• Table per CONCRETE Class (TPC): TPC demonstrates a single table per concrete class, but does not include the abstract class. Because of this, if an abstract class is inherited by many concrete classes, then the tables in all those concrete classes will have the same properties as that of an abstract class.

1. Lazy Loading

Pros

• When the relationships are not too high, use Eager Loading. So you can reduce further queries on the server by using Eager Loading.
• If you KNOW that related entities will be used everywhere with the main entity, use Eager Loading.

Cons

• Adding the extra lines of code to implement lazy load makes the code more complicated.
• It can affect a website's search engine ranking sometimes because the unloaded content is not properly indexed.

2. Eager Loading

Pros

• Upon executing the code, the system initializes or loads the resource.
• Additionally, related entities that are referenced by a resource must be pre-loaded.
• It is advantageous when resources need to be loaded in the background.
• It saves you time by avoiding the need to execute extra SQL queries.

Cons

• Since everything must be loaded to begin RUNNING, starting the application TAKES a longer time.

Choosing the right tool

• When you know you will use related entities with your main entity everywhere, use Eager Loading.
• You should use Lazy Loading WHENEVER you have one-to-many collections.
• Use lazy loading only if you are sure you won't need related entities right away.
• When you are unsure about whether or not an entity will be used, use explicit loading after you have turned off Lazy Loading.

• Lazy Loading: This process delays the loading of related objects until they are needed. During lazy loading, only the objects needed by the user are returned, whereas all other related objects are only returned when needed.
• Eager Loading: This process occurs when you query for an object and all of its related objects are returned as well. Aside from that, all related objects will load with the parent object automatically. When the INCLUDE method is used, eager loading can be achieved in EF6.
• Explicit Loading: Explicit loading occurs only when lazy loading is desired, EVEN when lazy loading is DISABLED. We must explicitly CALL the RELEVANT load method on the related entities to process explicit loading. When the Load method is used, explicit loading can be achieved in EF6.

Entity FRAMEWORK offers the FOLLOWING TYPES of loading: 

• EAGER Loading
• Lazy Loading
• Explicit Loading

Database concurrency in EF means that multiple users can simultaneously MODIFY the same data in one database. Concurrency controls help safeguard data consistency in situations like these.   

Optimistic locking is usually used to HANDLE database concurrency. We must first right-click on the EDMX DESIGNER and then change the concurrency mode to Fixed in order to implement locking. With this change, if there is a concurrency issue, we will RECEIVE a positive concurrency exception error.

This FIGURE SHOWS how stored procedure mapping details can be used in EDMX:

POCO stands for 'Plain Old CLR Objects'. YET, it does not mean these CLASSES are plain or old. A POCO class is DEFINED as a class that contains no reference to the EF Framework or the .NET Framework at all. In EF applications, Poco entities are known as available domain objects. 

POCO class is just like other normal .NET classes as these classes don't depend on any framework-specific base class, unlike the standard .NET class. Persistence-ignorant objects, or POCOs, support LINQ QUERIES, which are SUPPORTED by entities derived from the Entity Object itself. Both EF 6 and EF Core support POCO entities. 

.NET DEVELOPERS are allowed to work with relational data using domain-specific objects by object-relational mappers such as Entity Framework (EF) and Dapper. Performance-wise, Dapper is the King of Micro ORMs. 

• Dapper: A simple micro ORM, Dapper is considered a powerful system used for data ACCESS in the .NET world. As a means to address and open-source their issues, the Stack Overflow team created Dapper. Adding this NuGet library to your .NET project allows you to perform database operations. In terms of speed, it is the king of Micro ORMs and is almost as fast as using raw ADO.NET data readers.
• Entity Framework: It is a set of .NET APIs used in software development for performing data access. It is Microsoft's official TOOL for accessing data.

COMPARISON   

• According to NuGet downloads and performance, Dapper is the world's most popular Micro ORM. In contrast, Entity Framework is significantly slower than Dapper.
• In comparison to other ORMs, such as the Entity Framework, Dapper does not generate as much SQL, but it does an excellent job mapping from database columns to CLR properties.
• Since Dapper uses RAW SQL, it can be difficult to code, especially when multiple relationships are involved, but when a lot of data is involved and performance matters, it is worth the effort.
• Since Dapper uses IDbConnection, developers can execute SQL queries to the database directly RATHER than put data in other objects as they do in Entity Framework.

Objects in Entity FRAMEWORK are primarily assigned names using PLURALIZE and SINGULARIZE. This feature is available when ADDING a .edmx file. Entity Framework AUTOMATICALLY assigns the Singular or Plural coding conventions when using this feature. In convention names, an additional 's' is added if there is more than one record in the object. 

Below are the differences between Aadonet and Entity Framework: 

• A few data layer codes are created by Ado.Net that Entity Framework doesn't create.
• Entity Framework, unlike ADO.Net, GENERATES code for INTERMEDIATE LAYERS, data access layers, and mappings automatically. This results in a reduction in development time.
• On a PERFORMANCE basis, ADO.Net is more efficient and faster than Entity Framework.

DbSet: An entity SET is represented by a DbSet CLASS that can be used for creating, reading, updating, and deleting operations on it. Those DbSet type properties, which map to database tables and views, must be included in the context class (derived from DbContext).   

DbContext: It is CONSIDERED an ESSENTIAL class in EF API that bridges the gap between an entity or domain class and the database. COMMUNICATION with the database is its primary responsibility. 

The following steps will SHOW you how to retrieve DATA from a database in MVC (Model View Controller) using Entity Framework: 

• As a first step, we MUST create a new project.
• The next step is to add an Entity Framework reference from the NuGet package manager.
• Then, a new class has to be created within the model inside the table structure.
• After that, we are required to add a connection STRING in the web.config.connection. It should be MATCHED with the context.
• The next step is to open the Global.asax.cs class and add the new namespace of EF. We must then initialize the database.
• You will now need to right-click on the Controller folder and add a new controller, followed by a model reference in the section namespace.
• Last but not least, right-click on the controller's name and add the sections you want to retrieve.