.NET / EF Core - 60+ Practical Interview Questions

Apply Entity Framework Core's include to load villa and its amenities in a single query, joining villa and villa amenities via the navigational property and eliminating multiple database calls.

Use Include to load navigation properties and apply AsNoTracking for read-only retrieval, so EF Core does not track records and retrieval is optimized.

Updating a villa fails when the posted data lacks an id, causing EF Core to create a new villa. Add a hidden id field and update when villa.id > 0.

Improve dotnet core views by replacing magic strings with constants from a static detail file, group hidden properties, and enforce area, controller, and action ordering for a clean architecture.

Optimize the villa index action by loading villa amenities with a single include in Entity Framework Core, using AsNoTracking for read-only efficiency and a left join.

Improve the index action by replacing a multi-line if with a ternary operator for null or empty titles defaulting to dotnet mastery, and adopt string interpolation with the dollar sign.

The lecture shows how to fetch a villa's amenities by using include with no tracking to retrieve the first villa amenity for villa ID one, such as private pool.

Learn how explicit routing attributes create more straightforward, user-friendly URLs in MVC apps by adding a meaningful root that includes the controller name, avoiding reliance on controller and action names.

Refactor the home controller by moving shared formatting logic into a static details class, accessed through a using statement, to keep the controller clean and prevent duplicated code across controllers.

The home controller fetches villa by id and uses is null instead of == to avoid overridden equality; return error view or villa view.

Use a post endpoint to update a villa, save changes, and redirect to the index action, while validating the model state and catching the db update exception.

We compare two EF Core queries for villas and a single amenity, showing EF Core results in identical execution times.

The lecture demonstrates retrieving villa and amenity in the home controller with a where condition and order by. It emphasizes readability by formatting chained calls with one dot per line.

Learn to optimize an EF Core query in the home controller by applying take before to list to limit the results to ten, avoiding retrieval of all villas.

Shows how to optimize an EF Core query by applying split queries to load villa amenities, categories, pricing, and specialties without Cartesian explosion, and considers stored procedures as an alternative.

Inject the interface rather than the implementation to enable dependency injection and maintain loose coupling; this allows swapping service implementations without altering the controller.

Optimize the update pricing action by running three async services in parallel with Task.WhenAll to cut total execution time, highlighting that the duration is driven by the longest task.

Demonstrates that a break inside the inner loop only exits the inner loop, while the outer loop continues, producing the sequence 0, 1, and 2.

Optimize EF Core queries by materializing results with ToList before calculations, preventing deferred execution from causing multiple queries when building the villa summary view model.

Analyze all villa CRUD API endpoints and identify a redundant try-catch pattern. Implement a custom exception handling middleware in program.cs to return a unified 500 problem detail, simplifying controllers.

Spot opportunities to simplify code and reduce database calls by eliminating the count extension method, using the list count directly, and inline object initialization to avoid poor object initialization.

Inject ai services in the home controller index action and fix a null return in the interface to avoid a null reference exception and ensure the view model populates.

Update multiple villas in one query by using execute update async with a where condition to set comments, using Dotnet eight and improving efficiency over individual updates.

Identify and implement clean code improvements by replacing string concatenation in a loop with a string builder, then streamline villa summary view model initialization for better architecture.

Demonstrate how integer division of total price by total nights yields an incorrect average cost in the home controller's bookings loop, and explain converting to decimal before dividing fixes it.

Diagnose the index action bug by using grid.new grid to instantiate a grid, replacing the incorrect new keyword, and update the comment and booking date to datetime.now for display.

Retrieve all villas from the database and populate the villa summary view model, then replace single with first or first default to prevent multiple matches and show a random villa.

Learn how to replace a switch statement with a switch expression in C# to cleanly handle weekday and weekend logic, using or and not expressions for readable, maintainable code.

Retrieve villa amenities where price exceeds 350 and amenity ranking exceeds three using selectmany in entity framework core to optimize the SQL query.

Demonstrate debugging and fix villa details retrieval in the home controller by replacing first async with first or default async to avoid exceptions and redirect to the error page.

Discover why no-tracking queries prevent updating villa comments and saving changes, and learn to remove no-tracking so updates are tracked and saved.

Explore applying the dry principle to EF Core repositories by unifying find by id async endpoints with a shipment module enum and dynamic includes, reducing code duplication.

Refactor a block controller to depend on an interface, not a concrete service, and use dependency injection in Program.cs for loose coupling and try-catch error handling in the get endpoint.

Learn how to implement async endpoints in a .NET AI service, replacing void with Task to enable awaiting in controllers and improve clean architecture.

Use first or default with a predicate in EF Core to fetch a single record, letting EF Core consolidate the query; apply await with FirstOrDefaultAsync for async safety.

Move the variable that isn't modified outside the foreach loop to avoid recomputing the same value for each blog item, boosting performance.

The home controller builds new villa IDs by lane, totaling 15 villas; avoid modifying the collection during foreach and track the original ID count to prevent infinite loops.

Examine home controller's index action to compare count property and count() on a collection. Use the property for performance, and reserve the method for filtered queries like contains or name.

Learn how to override a base class method in a console app to print 'welcome from class B' within an a-b-c inheritance and the role of the override keyword.

Diagnose and fix null reference exceptions by adding a catch for the null reference and logging a message, preventing unhandled crashes and showing that a later catch won’t execute.

Explain how using the pre-increment operator ++i, instead of i++, ensures the index increments before use, producing the desired output of 10, 20, 30, 450 in a C# console app.

Learn to tailor day-of-week enum values in a console app by assigning nine to Friday, so Saturday auto-increments to ten and the output matches the target.

Discover how a console program computes the cube of a favorite number and distinguish value types from reference types by passing by address and updating the value.

Arrays in C# are reference types by default, so passing an array without ref yields the expected output; no modification is required to print the updated temporary array.

Explore how pre-increment versus post-increment affects a while loop, showing why x++ and ++x yield outputs like 11 and 20 versus 12 and 32 in the program.

Identify and apply code readability best practices in a .NET context, using indentation with tabs, spaces around operators, meaningful variable names, and cleaner object initialization with compound assignments.

Convert a string utility into a static string extension using the this keyword to trim and collapse spaces, then apply it in the home controller and application builder.

Learn how to read a file in a console app with stream reader, handle exceptions, and close the reader with a finally block when a using statement isn’t an option.

Demonstrate how sealing a method in C# prevents overriding in derived classes, making the base method final and triggering a compile-time error when inheritance attempts override.

Understand how throw affects stack traces in a console app and how preserving the original stack trace reveals the root cause and the true line of failure.

Apply projections with Entity Framework Core to fetch only the needed columns for a select list, improving performance. Use dot select to retrieve name and id instead of all columns.

The lecture demonstrates how to handle entity framework core tracking exceptions during post update by using AsNoTracking to avoid tracking retrieved villa, preventing the 'already being tracked' error.