.NET Interview Questions for 2026: 45+ Questions Across C#, ASP.NET Core, EF, LINQ, Blazor (CS New Grad Edition)

What .NET interview questions actually test in 2026#

.NET interview questions in 2026 test four things in roughly this order: whether you know C# at a level deeper than syntax, whether you understand the framework conventions (ASP.NET Core, EF Core, dependency injection) that production .NET runs on, whether you can talk through a small system design using .NET primitives, and whether you can hold an intelligent conversation about the .NET Framework vs .NET Core vs .NET 8+ history. The syntax floor is non-negotiable. The framework layer is where most interviews are won or lost. The history conversation is the senior signal even at the entry level.

The 2026 hiring environment for .NET roles has tightened differently than for Python or Java. Most greenfield startups use a non-.NET stack, which means .NET interview volume is concentrated at enterprise companies: regional banks, insurance carriers, healthcare networks, government contractors, defense, and the long tail of established mid-market firms that ran .NET Framework 4.x for fifteen years and are now migrating to .NET 8. These employers grade differently. They want candidates who can talk credibly about both the modern stack AND the legacy stack they still operate. A new grad who only knows .NET 8 reads as someone who's never going to be useful on the migration roadmap.

Distribution of question types most new-grad candidates report seeing in their .NET loops:

• 30-35% C# language internals (value vs reference, async/await, generics, delegates)
• 15-20% ASP.NET Core (middleware, dependency injection, controllers vs Minimal APIs)
• 15% Entity Framework Core (DbContext, change tracking, LINQ to entities)
• 10-15% LINQ (deferred execution, IEnumerable vs IQueryable)
• 10-15% OOP and SOLID (inheritance, interfaces, design patterns)
• 5-10% Blazor (Server vs WebAssembly, component lifecycle)
• 5% DevOps and CI/CD (build pipelines, NuGet, Docker)

The language-internals slice is the one most candidates underprepare. It is also the slice that disproportionately determines outcome.

How .NET interview questions differ from general coding interviews#

A general coding interview in any language tests algorithm fluency, problem decomposition, and communication. A .NET interview adds three dimensions: deep C# language knowledge, framework-convention fluency, and the history conversation. Three concepts in particular show up over and over in 2026 .NET interviews and rarely appear in interviews for other languages:

Value types vs reference types. A first-class concept in C# in a way it isn't in Python or JavaScript. The interviewer is testing whether you understand that a struct lives on the stack, a class lives on the heap, and the boundary between them (boxing) has a real performance cost. Almost every senior follow-up loops back to this.

The async/await state machine. Most candidates know how to write async methods. Fewer know that the compiler rewrites the method into a state machine, that Task is the return type representing a future value, and that ConfigureAwait(false) matters in library code to avoid deadlocks on UI threads. The state-machine question separates the candidate who used async from the one who understands it.

The .NET version landscape. "Walk me through the difference between .NET Framework, .NET Core, and .NET 10" is one of the most-asked .NET interview questions in 2026. Interviewers ask it as a litmus test for whether the candidate has been around the stack long enough to know what's deprecated, what's LTS, and what the company's migration path looks like. The version facts are on Microsoft's .NET support policy page: .NET 10 is the current LTS (released November 11, 2025, supported until November 14, 2028), while .NET 8 and .NET 9 both end support on November 10, 2026. Expect a follow-up about moving a .NET 8 service to 10 this year.

Three more concepts that round out the framework surface area: the ASP.NET Core middleware pipeline (order matters, and interviewers love asking what happens when you swap the order), EF Core's change tracker (the single biggest source of EF perf bugs new grads ship), and LINQ deferred execution (the IEnumerable vs IQueryable distinction that determines whether a query runs in C# or SQL). Deferred execution is the rule that a LINQ query doesn't run when you write it. It runs when you enumerate the result with ToList, foreach, First, or Count, and missing that is how the canonical EF pull-then-filter bug ships to production.

Two terms anchor most of these follow-ups, so pin them down early. Boxing is the hidden heap allocation that happens when a value type (an int, a struct) is assigned to an object or interface variable, and it's the perf trap senior interviewers fish for. A captive dependency is the bug you get when a Scoped service is injected into a Singleton, freezing the first instance for the app's whole lifetime. Say both back cleanly in your own words and you've answered half the C# and ASP.NET Core follow-ups before they're asked.

Honest call here: if you only have a weekend before the .NET round, drill async/await and EF change tracking first. They show up so often and trip up so many candidates that being fast on those two will compensate for being slow on three others. The fastest way to find out which two surfaces are still shaky is to run a mock .NET round and hear yourself answer out loud. The questions you fumble at speaking pace are the ones to drill, not the ones you can recite silently.

A specific case from the 2025-2026 cycle: a CS grad with 487 applications and 14 phone screens and zero offers over 11 months pivoted from web-startup-only targeting to mid-market enterprises running .NET 8. One weekend on async/await internals plus EF change tracking, two evenings on the version-history conversation, one .NET 8 ASP.NET Core API built from scratch. He landed two enterprise phone screens in week two of the pivot. The stack isn't the moat for new grads in 2026. The interview prep is.

The 45+ .NET interview questions you should rehearse#

What follows is a structured rehearsal set covering the seven categories that show up most. Each question has a sample answer outline. Not a full canned response, but the bones of what a strong answer covers. Adapt the language to your own voice. The structure is the load-bearing part.

C# language internals (10 Q)

.NET OOP and SOLID interview questions (7 Q)

ASP.NET Core interview questions (8 Q)

Entity Framework Core interview questions (6 Q)

LINQ interview questions (5 Q)

var topCities = users
    .GroupBy(u => u.City)
    .Select(g => new { City = g.Key, Count = g.Count() })
    .OrderByDescending(x => x.Count)
    .Take(3)
    .ToList();

Blazor interview questions (5 Q)

DevOps and CI/CD for .NET (4 Q)

How to prepare for a .NET interview (6 steps)#

A focused three-week prep plan, scaled for a CS new grad who took one C# elective but has never shipped a production .NET service. Adjust if your starting point differs.

1. Week 1: build a small ASP.NET Core API from scratch. Three endpoints, EF Core with SQLite, dependency injection, async controllers. Don't watch a tutorial. Read the official docs and write it yourself. The friction is the prep. When you hit an error, debug it; the debugging is how you learn. Total time: 8-12 hours.

2. Week 2: drill the C# language internals. Six concepts: value vs reference types, boxing, async/await as state machine, IDisposable + dispose pattern, generics with constraints, delegates plus events. 60-90 minutes per concept, with one written example. Read official Microsoft docs, not third-party blogs. The docs are the source interviewers reference.

3. Week 2 in parallel: memorize the .NET version history. .NET Framework 4.x (Windows, legacy). .NET Core 1-3 (cross-platform). .NET 5 (unification). .NET 6 LTS. .NET 7. .NET 8 LTS. .NET 9 STS. .NET 10 LTS (current; 8 and 9 end support November 10, 2026). Be able to state which is LTS, which the company likely runs, and how migrations work. The history question is almost certain in any enterprise interview.

4. Week 3: practice the canonical OOP and SOLID questions. Abstract class vs interface, virtual vs abstract vs override vs new, the five SOLID principles with one C# example each. Build a small class hierarchy and exercise each concept. Be able to write a 5-line interface and an implementation out loud, no IDE.

5. Week 3: run 3 timed mock interviews. End-to-end, 45 minutes each. First mock: C# and OOP. Second: ASP.NET Core plus EF Core scenario design. Third: Blazor plus LINQ depth questions. Narrate your reasoning out loud while coding. Silent coding is a known anti-pattern in live .NET rounds.

6. Morning of the interview: warm up with your cheat sheet. Five minutes on the top 20 concepts. The act of writing the sheet from memory was the prep. The sheet itself is the warmup.

.NET interview format by company type#

The same .NET language gets tested differently depending on the company. The breakdown for the five common company types running .NET in 2026:

Two patterns to notice. First, every company type tests C# at moderate-to-high depth. Even the legacy-heavy companies want to know you can work the modern language. Second, the legacy-questions slice concentrates at banks and insurance, where 15-year-old systems are still load-bearing. If you're interviewing for a bank, prepare to talk about .NET Framework 4.8, the migration path to .NET 8, and how you'd handle long-running systems with no test coverage. That conversation is the senior signal even at the entry level.

Tailor your prep to the column you're interviewing against rather than grinding all seven surfaces evenly. A bank round and a .NET-native SaaS round reward almost opposite preparation. If you want to drill against the exact stack version and question mix a specific employer runs before you walk in, see how unlimited targeted mock rounds are priced and rehearse the bank-migration conversation until you can say it in your own voice.

.NET interview questions for 5 years of experience#

With five years of .NET on your resume, interviewers stop asking what a feature is and start asking what went wrong when you used it. The questions in this guide still apply, but the follow-up changes from "define it" to "tell me about the time it broke in production." Expect to defend choices, not recite them.

Four areas carry most of a 5-year round:

• Async and threading in production. A deadlock from calling Task.Result on a UI or request context, a fire-and-forget task that swallowed an exception, a ConfigureAwait(false) call you added or removed and why. The interviewer wants a real incident, with the symptom, the cause and the fix.
• EF Core performance. Where you used no-tracking queries, how you found an N+1 query, and when you dropped to raw SQL. Microsoft's own efficient querying guidance says no-tracking queries avoid the change-tracking overhead when results are read-only, so "I use AsNoTracking for read paths" is a fair answer. "I use it everywhere" is not, because you lose change tracking on entities you meant to save.
• Dependency injection and configuration. Lifetimes, captive dependencies, and how you resolved a scoped service from a background job. Microsoft's dependency injection docs note that constructor-injecting a scoped service into middleware forces it to behave like a singleton, which is the same bug in a different place.
• Ownership of a migration or a design. Moving a service from .NET Framework 4.8 or .NET 8 to .NET 10, replacing a library, splitting a project. Say what you measured before and after.

If you have five years but little production incident experience, say that plainly and bring the closest thing you have: a side project you load-tested, or a bug you traced end to end. A specific, honest story beats a polished one that falls apart at the second follow-up.

.NET full stack interview questions#

A .NET full stack interview tests the whole path of a request: the browser, the ASP.NET Core API, the database and the way back. You are expected to be solid on the back end and conversational on the front end, whether that front end is Blazor, Angular or React. Most loops split into three parts, a C# and ASP.NET Core round, a database and EF Core round, and a front-end round.

Questions that come up often in the full stack version:

1. Walk me through what happens when a user submits a form. Strong answers follow one request: the browser sends it, the middleware pipeline runs in order, routing picks the endpoint, model binding and validation run, the service calls EF Core, EF generates SQL, and the response travels back as JSON or rendered HTML.
2. Where do you validate input, and why in more than one place? Client-side validation is for the user's convenience. Server-side validation is the one you can trust, because anyone can skip the browser and call your API directly.
3. How do you handle authentication across a separate front end and API? Know the trade-off between cookie-based sessions and token-based auth (such as JWT bearer tokens), and where each is stored on the client.
4. What is CORS and why did your front end get blocked? Browsers enforce the same-origin policy, so a page served from one origin cannot read responses from another unless the API allows it. Microsoft's CORS documentation covers how to allow specific origins in ASP.NET Core. The wrong answer is to allow every origin to make the error go away.
5. Blazor Server or WebAssembly, and why? See the Blazor questions above. The same trade-off applies here: server round-trips on every interaction versus a larger first download.
6. How do you deploy it? A build pipeline, a container or app service, a connection string kept out of source control, and a way to roll back.

If the front-end half is your weak side, pair this guide with the Angular interview questions or the React interview questions, and the SQL interview questions for the database round.

Technical architect interview questions for .NET#

Architect rounds for .NET roles ask for trade-offs, not definitions. This guide targets new grads, so treat this section as a preview of where the questions go, and expect to meet them in a first round only if the role is a stretch hire. The interviewer is listening for whether you name the cost of each option as well as the benefit.

The questions that recur:

• Monolith, modular monolith or microservices? A good answer starts from team size and deployment pain, not from fashion. Microservices add network calls, distributed failures and operational work, so you should be able to say what problem justified them.
• EF Core or a micro-ORM like Dapper? EF Core gives you change tracking, migrations and LINQ. A lighter library gives you control over the SQL. Many teams use both, EF for writes and raw SQL for a few hot read paths.
• How do you keep a slow downstream service from taking your API down? Timeouts, retries with backoff, circuit breakers and a queue for work that does not need an immediate answer.
• How would you migrate a .NET Framework system to modern .NET? Describe an incremental path, one assembly or service at a time behind a stable interface, with tests around the legacy code first. Ask which parts depend on Windows-only APIs, since those decide the order.
• What do you log, measure and alert on? Structured logs with a correlation ID, request latency and error-rate metrics, and one alert tied to what a user would notice.
• How do you choose between sync calls and messaging? Use a direct call when the caller needs the answer now, and a queue when it can wait and you want the work to survive a restart.

For the design-round format itself, System design basics for new grads walks through the framework, and these .NET questions are a specialization of it.

.NET interview cheat sheet#

A one-page reference of the top 20 concepts, organized for the morning-of warmup. The act of writing this from memory is the prep; carrying it into the interview is the safety net.

Memorize the top half; the bottom half is the polish.

How to handle a .NET question you've never seen#

The reality of a .NET interview is that you will hit at least one question you haven't seen. A behavior of the runtime, a niche EF feature, an edge case in async. The candidate who freezes loses the round. The candidate who reasons through it out loud often passes even when they get the wrong answer.

A four-step pattern for handling unfamiliar questions:

1. Restate the question in your own words. Slow down. Confirm what's being asked. Half the "tricky" questions become normal once you say them back. Example: "So you're asking what happens when an async method throws an exception that isn't observed before the Task is garbage collected. Would that crash the process or get swallowed silently? Let me think." That sentence buys you 10 seconds of thinking time and signals careful reasoning.

2. State what you know and what you don't. Don't pretend. "I know unobserved task exceptions used to crash the process in .NET Framework 4.0, but I think that changed in 4.5 and I'm not sure if .NET Core inherits the 4.5 behavior." Calibration beats confidence. Interviewers reward honest uncertainty more than they punish a wrong guess.

3. Reason from first principles. If you don't remember the answer, derive it. "Exceptions in an async method are captured into the returned Task. If no one awaits the Task, the exception sits there. The runtime needs to decide whether to surface it. In .NET Framework 4.0, it crashed the process. In 4.5+, I believe they made the default 'log and continue.'" That trail of reasoning is the work the interviewer is grading.

4. Test the hypothesis if you can. "Can I try this in a REPL or write a small repro?" is sometimes welcome and sometimes not, depending on the round. If allowed, do it. If not, walk through it on the whiteboard or in the editor with comments.

The pattern works because tricky .NET questions are rarely about memorization. They're about whether you understand the underlying model: the CLR, the async state machine, the EF change tracker, the DI container. Show your reasoning and you show your understanding.

Common .NET interview mistakes for CS new grads#

The seven most-reported mistakes from new-grad .NET interviews in the 2025-2026 hiring cycle, in roughly the order of frequency:

Treating C# like Java. Writing every loop as a for loop instead of foreach or LINQ. Using a List instead of an array when the size is known. Reaching for Hashtable instead of Dictionary<TKey, TValue>. Throwing generic Exception instead of specific subclasses. The interviewer sees: candidate learned C# in coursework but didn't internalize the idioms.

Confusing value types and reference types. Assuming a struct passed to a method gets mutated by the method (it doesn't, it's copied). Assuming a class returned by a method is a fresh object (it isn't, just the same reference). Boxing accidentally by assigning an int to an object variable and not realizing the perf cost.

Misunderstanding async/await. Treating async as multithreading. Calling Task.Result or Task.Wait in synchronous code and deadlocking the UI thread. Forgetting that an unawaited Task can throw an exception that gets swallowed. Marking a method async without using await inside (the compiler warns; new grads ignore the warning).

Shipping the IEnumerable-vs-IQueryable EF perf bug. db.Users.ToList().Where(u => u.Age > 18) pulls every row into memory before filtering. The interviewer sees the bug in 5 seconds and the candidate doesn't see it at all. Knowing where ToList sits in the chain is the difference between a tutorial-grade LINQ user and a production-grade one.

Not knowing the .NET version landscape. Conflating .NET Framework 4.8 with .NET 8. Calling .NET Core 'the new version' in 2026 (it was renamed to just '.NET' starting with .NET 5 in 2020). Not knowing which version is the current LTS. The version-history question is the litmus test for whether the candidate has been around the stack at all.

Forgetting middleware order in ASP.NET Core. Putting UseAuthorization before UseAuthentication and not understanding why every request returns 401. Putting UseEndpoints before UseRouting and not understanding why routing doesn't work. The middleware-order question is the canonical ASP.NET Core trap.

Misusing DbContext lifetime. Registering DbContext as Singleton (it's not thread-safe). Holding a DbContext beyond one unit of work (memory leaks, stale change tracker). Sharing a DbContext across requests (concurrency exceptions). AddDbContext defaults to Scoped for a reason; new grads don't always trust the default.

One thing I'd add from watching new grads do this: don't try to memorize all seven the night before. Pick the two that match your specific gaps (almost always the IEnumerable-vs-IQueryable bug and the .NET version history) and close those. The other five take care of themselves once the foundation is there.

Key terms#

Value type vs reference type

Value types (int, double, bool, struct, enum) store data directly. Reference types (class, interface, string, array, delegate) store a pointer to data on the managed heap. Value types pass by value; reference types pass the reference by value. Boxing happens when a value type is assigned to an object or interface, which triggers a hidden heap allocation.

async / await + Task

C#'s syntactic sugar for asynchronous programming. async marks a method that can pause; await pauses until an awaitable (Task, Task<T>, ValueTask) completes. The compiler rewrites the method into a state machine. Async is not multithreading; it's cooperative scheduling on top of the existing threading model.

IDisposable + using

IDisposable is the interface for releasing unmanaged resources (file handles, sockets, DB connections). The using statement guarantees Dispose runs even on exception. C# 8 added the using declaration syntax. The full dispose pattern handles both managed and unmanaged resources via a virtual Dispose(bool disposing) method.

Dependency injection (DI)

The design pattern where a class receives its dependencies through its constructor rather than creating them. ASP.NET Core has a built-in DI container with three lifetimes: Singleton (one for the app), Scoped (one per HTTP request), Transient (one per resolve). Captive dependencies (Scoped injected into Singleton) are caught by validation in development.

Middleware pipeline

The ordered chain of components in ASP.NET Core that handles each HTTP request and response. Each middleware can short-circuit, pass to the next via next(), or transform the response on the way back. Order matters: UseRouting before UseEndpoints, UseAuthentication before UseAuthorization.

EF Core change tracker + AsNoTracking

The in-memory record EF uses to track entity state (Added, Modified, Deleted, Unchanged). When SaveChanges runs, EF generates SQL based on the tracked changes. AsNoTracking skips tracking for read-only queries, saving the per-entity overhead. Most read paths in an API should be AsNoTracking.

IEnumerable vs IQueryable

IEnumerable<T> is an in-memory sequence; operations run via LINQ to Objects in C#. IQueryable<T> represents an expression tree that a provider (EF Core) translates into SQL. The classic EF perf bug is calling ToList() before Where(), which pulls every row into memory and then filters in C# instead of in the database.

Deferred execution

A LINQ query doesn't run when you write the expression; it runs when you enumerate the result (foreach, ToList, Count, First). Chaining multiple Where + Select + OrderBy operations composes into one operation that runs at materialization time, not at each step.

.NET Framework vs .NET Core vs modern .NET

.NET Framework 4.x: Windows-only, first released in 2002, last version 4.8.1, still in production at banks and insurance. .NET Core 1-3: cross-platform rewrite, 2016-2019. .NET 5: the unification, November 2020. .NET 6 LTS, .NET 7, .NET 8 LTS, .NET 9 STS, .NET 10 LTS (current since November 2025). Enterprise interviewers ask about the history as a litmus test.

Blazor Server vs Blazor WebAssembly

Blazor Server runs components on the server with a SignalR connection pushing UI updates. Low initial download, real-time UI, requires a persistent connection. Blazor WebAssembly compiles the app to WebAssembly and runs in the browser. Larger initial download, offline-capable, no round-trip latency. .NET 8's Blazor Web Apps mix both modes per-component.

Related guides#

• Python interview questions: the language most often paired with .NET on multi-stack roles, especially at insurance and healthcare companies running both stacks.
• AWS interview questions: the cloud stack most .NET-on-AWS roles test, and the answer to 'where would you deploy this?' in scenario design.
• System design basics for new grads: the framework for scenario-design rounds, which .NET architecture questions are a specialization of.
• Technical phone screen tactics: the round that tests .NET language depth under live observation.
• HackerRank tech interview guide: the platform most likely to host your .NET OA at an enterprise company.
• CoderPad live coding interview: the platform most likely to host your .NET live round.
• Mock interview practice: how to drill these .NET questions under realistic timing pressure.

About the author: Sam K. is the founder of InterviewChamp.AI, building AI interview prep for the new-grad CS market and writing about the modern interview gauntlet from the inside.

Originally published on InterviewChamp.AI