Entity Framework Essentials: Data Modeling and Queries Quiz Quiz

Explore key Entity Framework concepts with this quiz on data modeling, querying, relationships, and entity configuration. Assess your foundational knowledge and practical skills in managing data models and querying databases efficiently.

1. Defining the Primary Key

   Which property in a class will Entity Framework conventionally recognize as the primary key if it follows naming conventions?

   1. Index
   2. PrimaryKey
   3. Id
   4. PKID

   Explanation: Entity Framework uses conventions to identify primary keys, with a property named 'Id' or 'ClassNameId' typically recognized as the primary key. 'Index', 'PrimaryKey', and 'PKID' are not standard naming conventions, so Entity Framework will not automatically recognize them as primary keys. Using these other names would require explicit configuration.

2. Data Annotation for Required Field

   What data annotation attribute would you use to ensure that the 'Email' property of a 'User' entity cannot be null?

   1. [NotEmpty]
   2. [Required]
   3. [Mandatory]
   4. [StringLength]

   Explanation: The '[Required]' attribute ensures that the 'Email' property must have a value and cannot be null in the database. '[Mandatory]' and '[NotEmpty]' are not recognized data annotation attributes in this context. '[StringLength]' only enforces the maximum length, not the presence of a value.

3. Understanding Navigation Properties

   In an entity class, which type of property allows you to navigate to a related entity, such as accessing a 'Category' from a 'Product'?

   1. Index property
   2. Key property
   3. Navigation property
   4. Field property

   Explanation: Navigation properties define relationships and enable navigation between related entities, such as moving from 'Product' to its associated 'Category'. Key properties store unique identifiers, not relationships. Field and index properties have other purposes and don't facilitate entity navigation.

4. Eager vs Lazy Loading

   Which loading technique in Entity Framework retrieves related entities in a single query when the main entity is loaded?

   1. Eager loading
   2. Direct loading
   3. Lazy loading
   4. Deferred loading

   Explanation: Eager loading fetches related entities as part of the main query, reducing subsequent database trips. Lazy loading, on the other hand, loads related entities only when accessed, possibly resulting in multiple queries. 'Deferred loading' and 'Direct loading' are not standard terms in this context.

5. LINQ Query for Filtering

   If you want to retrieve all customers with the first name 'Alice' from a 'Customers' table, which LINQ method would you typically use to filter the data?

   1. OrderBy
   2. Select
   3. Join
   4. Where

   Explanation: The 'Where' method is used in LINQ to specify filter conditions, such as selecting all customers named 'Alice'. 'Join' is used for combining data from two sources, 'OrderBy' arranges data, and 'Select' projects data into a new form rather than filtering it.

6. Relationship Mapping

   How do you represent a one-to-many relationship between 'Author' and 'Book' entities in your model classes?

   1. Use a scalar property in both classes
   2. Include a collection of 'Book' in 'Author'
   3. Include a single 'Book' in 'Author'
   4. Add a collection of 'Author' to 'Book'

   Explanation: A one-to-many relationship is represented by including a collection of 'Book' objects in the 'Author' entity. Including a single 'Book' does not represent multiple books. Adding a collection of 'Author' to 'Book' would imply a many-to-many relationship. Scalar properties alone do not establish navigation between entities.

7. Updating Entity State

   Which context method should you call to save all changes made to tracked entities in the database?

   1. SaveChanges
   2. ApplyUpdates
   3. CommitAll
   4. Persist

   Explanation: 'SaveChanges' applies all updates to tracked entities in the data context to the database. 'CommitAll', 'Persist', and 'ApplyUpdates' are not valid context methods in this framework for saving changes, so using them will result in errors or no effect.

8. Database Generation Strategy

   To let the database automatically generate unique key values for new entities, which property configuration should you apply?

   1. Identity
   2. Static
   3. Manual
   4. Sequenced

   Explanation: Setting the property to 'Identity' configures it for automatic database-generated unique values, commonly used for primary keys. 'Manual' means the developer must provide values, while 'Static' isn't a recognized configuration. 'Sequenced' is a different term and not specifically used for automatic key generation in this context.

9. Query Syntax Selection

   Which syntax allows you to write queries in a style similar to SQL but using strongly typed objects in the entity framework?

   1. LINQ query syntax
   2. Procedural queries
   3. DDL statements
   4. Raw SQL commands

   Explanation: LINQ query syntax provides a SQL-like way to query data using strongly typed objects, offering both readability and type safety. Raw SQL commands involve writing direct SQL, not object-oriented code. DDL statements define or modify database structures, not for querying data. 'Procedural queries' is not a standard term in this context.

10. Tracking Changes

    Entity Framework automatically keeps track of changes to entity objects during a session by default using which feature?

    1. Logging
    2. Auditing
    3. Change tracking
    4. Snapshotting

    Explanation: Change tracking is the feature that allows the framework to monitor changes made to entity objects during a session. 'Snapshotting' is related to taking point-in-time copies of data, 'Auditing' tracks user actions for compliance, and 'Logging' typically refers to recording application events, making them less relevant here.