ASP.NET Core Entity Framework Core 3

Question 1

What is the N+1 query problem in Entity Framework Core?

Accepted Answer

Executing one query to fetch a list then N additional queries for each item's related data

Answer

N+1 occurs when related entities are loaded via lazy loading in a loop, generating one query per item instead of a single JOIN.

Question 2

Which EF Core method allows executing raw SQL and returning entity results?

Accepted Answer

FromSqlRaw()

Answer

FromSqlRaw() composes a raw SQL query that returns tracked entity instances mapped to the DbSet entity type.

Question 3

What does the [Required] data annotation do on an EF Core entity property?

Accepted Answer

Marks the database column as NOT NULL and adds model validation

Answer

[Required] configures the column as NOT NULL in the schema and also participates in ASP.NET Core model validation.

Question 4

Which EF Core feature automatically creates the database schema from the model without migrations?

Accepted Answer

EnsureCreated()

Answer

EnsureCreated() creates the schema if the database does not exist, but bypasses migrations — use only for testing/prototyping.

Question 5

How do you configure a one-to-many relationship in EF Core Fluent API?

Accepted Answer

HasMany().WithOne()

Answer

HasMany().WithOne() defines a one-to-many relationship, with HasMany on the principal and WithOne on the dependent side.

ASP.NET Core Practice Test