Top 20 Entity Framework Interview Questions – MUST HAVE

By | June 22, 2016
Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInDigg thisPin on Pinterest

This post is about Entity Framework Interview Questions that will explore various features, concepts and FAQs regarding Microsoft Entity Framework. It’s basically a collection of most frequently asked Entity Framework Interview Questions for developers. You can also explore some practical solutions implementing Entity Framework here:

You are working with WebDevTutorial and building an ADO.NET Entity Framework application for a client. You need to validate the conceptual schema definition language (CSDL), store schema definition language (SSDL), and mapping specification language (MSL) files. Which Entity Data Model tool can you use? (Each correct answer presents a complete solution. Choose all that apply.)

  • A. EDM Generator (EdmGen.exe)
  • B. ADO.NET Entity Data Model Designer
  • C. Update Model Wizard
  • D. Entity Data Model Wizard
  • E. All of Above
  • F. None of Above

For a complete online test and Practice Exams on Web Technologies, Click Here.

 Correct Answer: B, D

Udemy

Entity Framework Interview Questions List

More Entity Framework Interview Questions for beginners and Experienced

What is Entity Framework?

Microsoft Entity Framework (EF) is an Object Relational Mapping framework that provides an abstraction layer (a kind of mapping) between two incompatible systems (i.e. Object oriented programming languages with Relational databases). It enables us to interact with relational data in an object oriented way, meaning we can retrieve and manipulate data as strongly typed objects using LINQ queries.Microsoft Entity Framework

Microsoft introduced Entity Framework with .NET Framework v3.5 Service Pack 1 supporting basic Object Relational Mapping support but later EF4 was introduced as second version aligning with .NET Framework v4.0.
Back to top

What are the advantages of using Entity Framework?

Main advantages of Entity Framework are:

  • Separation of Concerns (SoC).
  • LINQ is used as a common syntax for all object queries.
  • Code Auto-Generation.

Back to top

What is Entity Framework(EF) Core?

Entity Framework 7 rebranded as Entity Framework Core 1.0 is basically an object-relational mapping framework that allows us to communicate with database using .NET objects. It’s a lightweight, open-source and extensible framework for targeting .NET Core applications.Entity Framework Core

Entity Framework Core 1.0 has following additional features:

  • Cross Platform i.e. can work with .net core application built for MacOS or Linux.
  • Designed for disconnected/web services.
  • Entity Framework Core is cloud optimized.
  • EF Core is Device Optimized as being lightweight can work with SQLite.
  • Support for relational and non-relational databases.
  • EF Core also has Fluent API that enables a user to override the OnModeCreating strategy on a user’s context and makes it easy to figure the convention model.
  • Built-In convention that effectively builds an initial model based on the entity classes.
  • The EF Core features data annotations that are added to entity classes or properties to influence the EF model.
  • It also has Snapshot change tracking properties based on recording the initial values of an entity as it is retrieved from the database.
  • Notification change tracking enables a user’s entities to signal the change tracker in case property values are modified.
  • Connection resiliency that automatically retries any failed database commands. Connection resiliency comes in handy for connection to SQL Azure which is prone to transient failures.

There are many key features those were available in EF 6.x but not included in Entity Framework Core 1.0.

  • No Lazy Loading.
  • Group By Translation – If query includes a group by clause, it will be omitted.
  • Not Supporting stored procedures.
  • No Graphical Modeling Tools supported.
  • Spatial Data Types (a wrapper around a COM library).
  • Simple Command Interception.

Back to top

What is the Nuget Package console command to install Entity Framework, if it’s not there in you project at that time?

Following is the Nuget Package console command to install Entity Framework:

Install-Package EntityFramework -Version 6.1.1Install Entity Framework -Version 6.1.1
Back to top

How to Install Entity Framework via NuGet Package in Visual Studio?

It’s quite simple to install Entity Framework via Nuget for our project in Visual Studio. For example, If I have just created a new project and want to install Entity Framework, below step by step approach will be helpful.

  1. Right click on the project and choose “Manage NuGet Packages…”.Manage NuGet Packages
  2. On Installation page, choose “Browse” Tab from top left and then enter “Entity Framework” in search box below that and click on search icon. It will list down all Entity Framework related results below. Installing Entity FrameworkAs you can see, we have selected Entity Framework and all details (including version, author, License, Date Published etc.) of the selected item are displayed in right area.
  3. In above screenshot, click on Install button. It will ask for a Review Changes going to be done, confirm by clicking “YES”.Review Install EF
  4. It followed by a License Acceptance confirmation. Just confirm by clicking “I Accept”.License Acceptance EF
  5. Once you accept the License, it will complete the installation displaying details in Visual Studio Output Window as shown in below screenshot.Entity Framework Installed Finally, you can see the successful installation message in Output Window. Once the installation is done successfully, you can see EntityFramework and EntityFramework.SqlServer in References of our project.

Back to top

Where do we use Virtual classes in Entity Framework DbContext Models?

We use Virtual classes in Entity Framework in context class where we define DBSet of corresponding table. As we can see easily in below code sample for Students and Departments:
Entity Framework Interview Questions Virtual Classes
Back to top

Entity Framework uses DbContext, How is it different from Object Context?

DbContext can be used for code first while Object Context doesn’t. It exposes the most commonly used features of ObjectContext.
Back to top

What’s new in Entity Framework 6?

  • Customizing Code First Conventions.
  • Logging of database commands.
  • Stored Procedure Mapping.
  • Asynchronous Queries and Save support.

Whats New In EF6

With EF6, in applications with lots of tables and relationships defined, our context objects open faster. We should also be better insulated from dropped connections (at least, if the drop is transient and not permanent — nothing is going to help there).  EF6 also generates SQL faster from LINQ queries than before (though it’s the same SQL that’s being generated as in earlier versions of EF, so your actual data access won’t be any faster or slower).
Back to top

Can we access a model in Entity Framework without primary key defined?

No, but we can access data.

Using Primary Key:

Student student = db.Students.Find(id);

Without Primary Key:

Student student = db.Students.Where(x=>x.StudentName==”Ahmad”);

Back to top

Why do we use Lazy Loading in Entity Framework?

Entity Framework facilitates us to avoid huge, deep, highly-relational queries, so that the data will not heavy on the web.

Note: As by default, lazy loading option is enabled in Entity Framework but that can cause major performance issues in some scenarios as below:

As for above scenario, student.Department will load department from SQL Server by firing a new SQL query for each iteration and it’s a performance degradation in case of large number of records.
We can disable Lazy loading (or in other words, enable eager loading) by using the following code:

Back to top

Why DB Context models object disposal is important in Entity Framework?

Until it’s disposed, it will be holding resources that aren’t in. If not disposed then Garbage collector will free the space but in some instance it holds up.

Calling dispose method to clear memory.Dispose in Entity Framework
Back to top

Can we do an insertion and deletion at the same block of code and then Apply save changes to them in a statement in Entity Framework?

Yes, WE CAN by using the below piece of code:

Save changes in Entity Framework

Here the student record will insert to db but not physically. When we call SaveChanges method then it actually insert in db and commit the transaction. If we delete before committing transaction nothing will change in database.
Back to top

What are the development approaches are supported in Entity Framework?

Following are the development approaches available in Entity Framework. Implementation of each approach is given in detail in separate Entity Framework Tutorial:

  • Code First Approach – where code defines the database. Entity Framework handles creation. A complete detailed implementation of Entity Framework Code First Approach here.
  • Database First Approach – regular approach used where database is first created or already exists.
  • Model First Approach – where model is drawn first that further generate database scripts.

Development Approaches in Entity Framework
Back to top

If we have not followed proper conventions in Code First approach, then how we can mark a field/property as primary key?

An important point to remember about EF Code First approach; we have to follow proper convention for a primary key, means Entity Framework expects ID combined with Entity Name. In our case, above referred Code First Example, we have two entities (i.e. Category and Product) and for both of these entities, we used proper convention for primary key i.e. CategoryId and ProductId.

But in case we used something different i.e. “UniqueCategoryIdentifier” or “UniqueProductIdentifier”, then we have to tell that this is our primary key column and this can be done using a simple attribute i.e. “Key” as follows:

If we don’t follow the convention as well as not using the “Key” attribute, then will end up with following error.

Note: It’s always recommended to use proper convention or use “Key” attribute to tell Entity Framework about our primary key field.

Back to top

How we can enforce number of characters (minimum or maximum) for a field using Entity Framework Property Annotation method?

We can easily use property annotation of MinLength and MaxLength to enforce minimum or maximum number of characters for a specific field respectively. For example, If we want to have minimum and maximum number of limit for CategoryName field for Category Entity (say minimum 10 and maximum 100 characters). Below is the way to use, MinLength and MaxLength:

Back to top

How we can use a property for an Entity that is not mapped to database in Code First Approach?

In Code First Approach, all properties are normally mapped to database. But in certain scenarios, if we don’t want a specific property to be mapped to database, Entity Framework provides us with NotMapped attribute for annotation.

Let’s take a practical example, we have an entity i.e. Product and we want to have a ProductCode that will not be mapped to database. So, we will do the following to achieve in Code First Approach.

Back to top

What is the query syntax we use to query an ADO.NET Entity Data Model?

We can use LINQ to Query ADO.Net Entity Framework. For Example:

Entity Data Model
Back to top

Is LINQ a feature of Entity Framework?

Yes, following is the example to get student record from Section A.

LINQ feature in EF6

The same in Entity Framework:

Student student = db.Students.Where(x=>x.Section==”A”);
Back to top

Does Default New Project Creation under Internet Template Category of ASP.NET MVC have any DB Context Ready while creating the project?

Yes, There is, as we can see in the below screenshot:Template Category For MVC
Back to top

If you provide the Primary Key value while inserting record to Entity Framework, will that execute fine, or will it throw an error while the adding statement?

Yes it will threw error if same a record present with same data. If identity is set then it will give error in any case.Insert In EF6
Back to top

What are the properties or Database Elements get copied in Dataset when Clone method is used?

It will create a new object with same properties with a new instance.Clone Method in EF6
Back to top

What is the role of a Self-Tracking Entities?

Self-tracking entity allows you to add code generated item:Self Tracking Entities in EF6
Back to top

Can you describe the feature of split entity in Entity Framework?

Entity splitting gives us the ability to take an entity in our model and split this entity into multiple database tables. When we query an entity, Entity Framework will create a query that Automatically joins the related physical tables for us.
Back to top

What is the role of Entity Container in Entity Framework?

Entity container is a logical grouping of entity sets, association sets, and function imports.  The following must be true of an entity container defined in a conceptual model:

At least one entity container must be defined in each conceptual model.  The entity container must have a unique name within each conceptual model.

Entity Container in EF
Back to top

Do we need to define any assembly references of entity framework if we use in web.config file?

Yes, that is necessary:web.config for Entity Framework

Back to top

More Entity Framework Interview Questions including Entity Framework Core

LINQ to SQL Vs Entity Framework?

Following table clearly explains the difference between LINQ to SQL Vs Entity Framework:

Entity Framework LINQ to SQL
Work with any database including SQL Server, Oracle, MySQL, DB2 etc. Works but limited to SQL Server.
Entity Framework works well in enterprise scenarios where requirement is to develop a loosely coupled application. LINQ to SQL is good in rapid application development scenarios but follows a tightly coupled approach.
Entity Framework maintain a conceptual model that actually maps to storage model using a mapping. So, it’s possible that multiple EF classes map to one table or multiple tables map to one EF class. A LINQ Entity directly maps to one SQL Server table only. In order to maintain a relationship, it generates a .dbml file.
Can generate database from model and it’s a key feature. Generate database from model is not possible.
Back to top

How to handle transactions in Entity Framework 6

Transaction being a single unit of work that are either successful or failed has really important for an application that is developed using Entity Framework. Entity Framework supports transactions in following ways and this Entity Framework 6 Interview Questions demonstrate the same:

The “SaveChanges()” method in Entity Framework operates within a transaction and saves results of the work. This is how the data integrity is being ensured.

In Entity Framework 6.0, two new APIs are used to maintain the transaction:

1. DbContext.Database.BeginTransaction: Below we can find source code to understand that how different operations are combined within the same transaction and further are all committed or rollbacked. This method also allows us to specify the isolation level for the transaction.

2. DbContext.Database.UseTransaction: It allows DbContext to use a transaction that was stated outside of the Entity Framework. It means using this API we can use any existing transaction with Entity Framework.

It is used when sometimes we must use an existing transaction that is started outside of the Entity Framework.

Back to top

  • Learn ASP NET MVC 5 step by step [Maruti Makwana, Corporate Trainer] 28 Lectures, 2.5 Hours Video, Intermediate Level
    Very easy to learn video series on Asp.Net MVC 5 Specially for those who are familiar with Asp.Net Web forms.
  • AngularJS for ASP.NET MVC Developers [Brett Romero] 10 Lectures, 1 hour video, Intermediate Level
    The Fastest Way For .NET Developers To Add AngularJS To Their Resume
  • ASP.NET with Entity Framework from Scratch [Manzoor Ahmad, MCPD | MCT] 77 Lectures, 10 hour video, All Level
    Latest approach of web application development
  • Comprehensive ASP.NET MVC [3D BUZZ] 34 lectures, 14 Hours Video, All Levels
    From zero knowledge of ASP.NET to deploying a complete project to production.

Concluding Notes:

Again, this is my prepared list of important Entity Framework Interview Questions but reader can suggest/contribute more related concept area. I’ll be more happy to add those questions/concepts and update the Entity Framework Interview Questions list.

More Related Articles:

Top Web Developer Interview Questions and Answers Series:

Udemy

ASP.NET MVC Jobs [Updated Daily]

Top ASP.NET MVC Jobs

Developer, C#, .NET, MVC
Source: Logic20/20
Details: Developer, C#, .NET, MVC. C#, .NET framework (ASP.NET MVC, Entity Framework). Solid knowledge of C#, .NET framework (ASP.NET MVC, Entity Framework)....  More
13 days ago

Seattle, WA 98115 13-June-2017

Dot Net Developer
Source: Indeed
Details: ASP.NET MVC, JQuery, Entity framework, HTML programming. Develop enterprise web or desktop applications using *Microsoft .NET, ASP.NET, C#, application...  More
18 days ago

Redmond, WA 07-June-2017

Principal Engineer
Source: Indeed
Details: C#, .NET, ASP.NET MVC, WCF, Rest, WebAPI, HTML5, AJAX, JSON, JQuery, ServiceBus, RabbitMQ, TeamCity and similar....  More
30+ days ago

Austin, TX 22-May-2017

ASP.NET MVC Web Developer
Source: Cardinal Intellectual Property, Inc
Details: ASP.NET MVC Web Developer. Strong or expert knowledge of C#, JQuery, JavaScript, Knockout JS, ASP.NET MVC, MSSQL....  More
2 days ago

Evanston, IL 23-June-2017

Senior .Net Developer
Source: Indeed
Details: Sitecore (including Helix and MVC), C#/.NET, ASP.NET MVC, NPM, jQuery, CSS, SASS, GIT & SVN, CI, SQL, DB2, and REST service architecture....  More
4 days ago

Wilton, CT 21-June-2017

.NET MVC Web Developer
Source: R. Watson & Associates, Inc.
Details: Experience with ASP.NET MVC, SQL, HTML and JavaScript at a minimum. We are looking to expand our team by hiring a .NET MVC Web Developer....  More
10 days ago

Talent, OR 16-June-2017

.NET Developer
Source: Inforeem
Details: 3.AngularJS, ASP.NET MVC, JQuery, HTML5. We are looking for strong profiles in .NET/C#, MVC (data Structure, Algorithm), SQL queries....  More
24 days ago

Redmond, WA 02-June-2017

ASP.NET MVC Developer
Source: Net ESolutions Corporation (NETE)
Details: Design and develop new features and/or maintains existing applications developed on ASP.NET MVC. NETE is seeking a highly motivated, flexible, organized, and...  More
23 days ago

McLean, VA 03-June-2017

C# .Net Developer (Locals Only)
Source: Indeed
Details: 3.AngularJS, ASP.NET MVC, JQuery, HTML5. 1.Good in C# and Microsoft .Net....  More
3 days ago

Redmond, WA 22-June-2017

C# .Net Developer
Source: Indeed
Details: Responsibilities include: Rewrite an existing COTs system in accordance with CMS’ Agile XLC framework on site at Security Blvd. Under the guidance of the  More
3 days ago

Windsor Mill, MD 21244 22-June-2017

.Net Developer - Web Services - Web API - SQL
Source: Indeed
Details: 4 to 7+ years experience with software design and development (including the Microsoft application development framework) preferably C#, ASP.Net, ASP.Net MVC....  More
9 days ago

Minneapolis, MN 16-June-2017

Xamarin Dotnet/.Net Developer
Source: Indeed
Details: Strong knowledge and working experience of NET MVC. Solid experience on C#, Xamarin - Xamarin including Xamarin.iOS and Xamarin.Android, JavaScript, Mobile...  More
9 days ago

Miami, FL 16-June-2017

.NET Software Developer Fin Tech
Source: Indeed
Details: Experience with ASP.NET MVC. Would you enjoy working in a cutting edge C# environment and programming with technologies like C# 5.0, MVC 5, ASP.NET Core and...  More
9 days ago

Evanston, IL 16-June-2017

.NET Software Developer - Cambridge, MA
Source: Indeed
Details: Exposure to ASP.NET MVC framework:. Good understanding and exposure to ASP.NET MVC framework. .NET Software Developer....  More
11 days ago

Cambridge, MA 15-June-2017

C# .Net Developer
Source: Indeed
Details: MVC:. Solid understanding of MVC architecture and frameworks. Experience in enterprise web application development using Microsoft technologies(C#, ASP.NET MVC,...  More
12 days ago

Santa Clara, CA 13-June-2017

Software Developer
Source: Indeed
Details: Experience with Asp.net MVC, Razor, .Net Core, Html, CSS, XML, XSLT, XPath, AJAX, Web API (is a plus). Software Developer (Mid-Level)*....  More
3 days ago

Austin, TX 78730 22-June-2017

Software Developer
Source: Indeed
Details: Knowledge in Visual Studio 2005-2013 and .NET Framework 2.0 - 4.5.1, ASP.NET MVC 5.0, VB 6.0/.NET, C, C++, C#, Java, Tomcat, Transact-SQL, HTML, XML, JavaScript...  More
4 days ago

San Juan, PR 21-June-2017

ASP.NET Web Developer
Source: Sandhills Publishing
Details: ASP.Net MVC Framework, Object Oriented Programming, Web Services and RESTful APIs, XML, MS SQL, HTML, CSS, TFS or Version Control familiarity....  More
5 days ago

Lincoln, NE 20-June-2017

Applications Developer 3 - .NET
Source: Metropolitan Council
Details: Experience with any JavaScript based MVC or MVVM framework, such as:. Work in an environment that allows you to have a life outside of work and does NOT require...  More
17 days ago

Minneapolis, MN 08-June-2017

Software Development Engineer - Full Stack - Contract
Source: Neal Analytics
Details: Middle tier (ASP.NET MVC / Java). Familiar with MVC, Entity Framework, ASP.NET. We are supporting a well-known cloud platform for one of the largest software...  More
26 days ago

Redmond, WA 31-May-2017

SQL Lead Developer
Source: Indeed
Details: Understanding of ASP.NET MVC 5 including Bootstrap, Razor views and view models, as well as controllers and models. Are you a SQL Wizard?*....  More
9 days ago

Mooresville, NC 28117 16-June-2017

Junior Software Engineer
Source: Indeed
Details: Oracle 11g (or higher), SQL Server 2012 (or higher), AngularJS framework, HTML/HTML5, ASP.Net / ASP.Net MVC. Responsibilities of the Junior Software Engineer:....  More
2 days ago

Prescott Valley, AZ 86314 23-June-2017

Launch and Range Subject Matter Expert (Software Engineer)
Source: Sigmatech, Inc.
Details: Experience in software development utilizing C#, MVC, JavaScript, .NET., Visual Studio, and SQL. Proficiency in C#, ASP.NET MVC, Web API, MSSQL Server, MySQL,...  More
3 days ago

Colorado Springs, CO 80901 22-June-2017

Software Developer
Source: Indeed
Details: .NET Stack experience (C#, ASP.NET MVC, MS SQL Server). We are seeking a talented and motivated software developer to join our development team....  More
9 days ago

San Diego, CA 16-June-2017

Software Engineer. Net
Source: Indeed
Details: JQuery, SSRS, Design Pattern, ASP.NET MVC, and UML, Microsoft Test Manager. C#, ASP.NET with MVC, SQL Database 2012/2014, and Business Analysis, Report Services...  More
5 days ago

Boca Raton, FL 33487 21-June-2017
Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInDigg thisPin on Pinterest