Entity framework is a new Microsoft technology that allows programmers to connect to databases using data model objects. Instead of old data connections that required the developer to work with database connections, Entity framework allows the developer to create data model classes that do all of the backend work and leaves the developer with only data classes. These classes represent the tables in your database, so you can more easily understand your data and its relationship with other database objects.
Many .NET framework companies require you to understand Entity framework before you can work with their products. You will probably need to answer some questions in your technical interview. Technical interviews are stressful and hard, especially if you are new to the industry. If you aren’t used to technical interviews, you might not know what to expect when you walk into the interview room. Here are some common Entity framework interview questions you might come across in the field.
1) What is “code first” in relation to Entity framework?
Entity framework uses the process of “code first” that maps database tables to data models. The data models in your .NET project are actually classes that represent the structure of your database tables. This code is used to work with your database, so you don’t need a direct connection to your database in each of your class methods.
2) What is the difference between old ADO .NET and Entity framework coding techniques?
When you used ADO, you connected to the database and had to define a stored procedure or query to retrieve data. With Entity framework, you don’t have to be “blind” when it comes to your tables. ADO did not allow you to get the table structure. With code first, you already have the table structure and Entity framework connects to the database and hides any connection processes. With Entity framework, you’re more aware of the database structure, which helps you avoid any coding mistakes. In addition, if the table structures change, Entity framework updates the data models for you during a refresh.
3) What is LINQ?
Language-Integrated Query (LINQ) is a way to query data without cumbersome stored procedures. Previously, programmers needed to create stored procedures and then call these stored procedures from their code. With Entity framework, you can pull data and query it using language similar to SQL.
4) How is data retrieved?
The difference between older retrieval methods and current Entity framework retrieval methods is that you can now (with Entity) retrieve data as objects. The objects represent the tables (or linked tables) in your database. Instead of iterating through several columns and rows, you just use your class data models. For instance, if you have a table named “users,” you can use the “users” class instead of working through each data set after your query.
5) Can you run SQL statements in an Entity framework environment?
Yes, you can also run SQL query statements. You can use the “ExecuteStoreCommand” method to run SQL on your database. This is usually a secondary option from running simple LINQ on your Entity framework code. You can also run stored procedures from a database.
6) How do you create a database model?
Visual Studio has a database modeler available. You can create a database model from scratch, or you can query the database for the models. If you have a database already, you simply pull the database structures from your code and Entity framework will automatically set up the class data models.
7) Does Entity framework support primary and foreign keys?
Yes, Entity framework supports both types of primary and foreign keys. You can define these in your database tables and import them to your model classes. If you don’t already have a database set up, you can create these keys in your data model classes and their respective data modeling classes.
8) How do you mark a data column as required by the database?
You can “decorate” your data models. The “Required” decoration marks a field as required. Before a user can submit the data to the database, the user must have this field entered. You can also auto-generate required fields in your code, so the code automatically adds the required data.
9) What is lazy loading?
Lazy loading is a way to return only objects that are used. When you query the database model, lazy loading only returns the immediate tables needed by the user. All related tables are returned when they are used. This means you can reserve memory and storage when you work with large programs. It also means that objects are created until you need them, so it makes your program faster.
10) What is eager loading?
Eager loading is the opposite of lazy loading. When you query for objects, eager loading returns all of the objects including the related objects. For instance, when you query a list of customers and orders, eager loading loads all objects including the customers and the orders instead of just what you originally need (customers).
11) What is a navigation property?
A navigation property points to related tables in your database model. For instance, if you have a customer table that relates to the orders table, the navigation property points from the customers table to the orders table. While the primary and foreign keys are physical properties of the table, the navigation properties are a logical part of a data model. When you view the Entity framework model, you can view the navigation properties to better understand the structure of your tables.
12) What is a scalar property in your data model?
A scalar property is similar to a scalar property in the database. A scalar property points to one location in the table.
13) What is a complex data type?
A complex data type occurs when you need to point to another data object from one data object. For instance, if you have several tables that require an address, you can turn those addresses into a table of addresses. You then point your address columns to the new address table, which creates a complex data type. You will likely have complex data types in every .NET Entity framework project, because it makes it easier to relate one table and data model to another without creating cumbersome code.
14) Overall, what is Entity framework?
Entity framework is a type of ORM (object relationship model) that connects classes with database objects. It makes it easier to work with databases and tables without worrying about columns and rows. ORM makes it easier for you to query databases using LINQ, and you do not need to worry about your database connection. Additionally, you can create programs that are unaware of the database and its connection or type (Oracle, SQL Server or MySQL). Entity framework takes care of all of the back-end connection so you can worry about the queries and data.
These are just a few of the common questions you need to know when you go for jobs in the .NET development industry. Entity framework is a comprehensive tool when you want to work with databases in your .NET development platform. You can’t guarantee that any one question will be asked when you go for an interview, but you can prepare for some of the common questions that are regularly asked by interviewers.