Interview Q&A

Answer: IConfiguration is automatically registered and injected via constructor. public MyService(IConfiguration config) { var key = config["MyKey"]; }

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

dd custom validation and authorization filters using .AddEndpointFilter().

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

SP.NET Core provides structured logging via ILogger<T>.

public class MyService
{
private readonly ILogger<MyService> _logger;
public MyService(ILogger<MyService> logger) => _logger = logger;
public void DoSomething() => _logger.LogInformation("Action

performed");

}

Yes—result filters can wrap or modify responses.

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: Occurs when two services depend on each other directly or indirectly. 🛠 Fix: Refactor to remove circular reference Use Lazy&lt;T&gt; or factory injection Split responsibilities

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

filter that tracks performance of controller actions:

public class ProfilingFilter : IAsyncActionFilter
{
public async Task OnActionExecutionAsync(

ctionExecutingContext context, ActionExecutionDelegate

next)

{
var sw = Stopwatch.StartNew();
var result = await next();

sw.Stop();

Console.WriteLine($"Action took

{sw.ElapsedMilliseconds}ms");

}
}

Use a mocking framework like Moq:

var mockService = new Mock<IMyService>();
mockService.Setup(s => s.Get()).Returns("test");
var controller = new MyController(mockService.Object);

Mocking helps isolate the unit of work and test behavior independently.

MVC & Razor Pages

• MVC (Model-View-Controller) is a pattern for organizing code into:
• Model: Data and business logic
• View: UI rendering
• Controller: Input handling and app flow
• Built on a modular, cross-platform framework.
• Uses dependency injection by default.
• Unified Web API + MVC pipeline.
• Lightweight and middleware-based request processing.

How does it differ from MVC in

“older” ASP.NET?

• MVC (Model-View-Controller) is a pattern for organizing code into:
• Model: Data and business logic
• View: UI rendering
• Controller: Input handling and app flow

🔹 Key differences in ASP.NET Core:

• Built on a modular, cross-platform framework.
• Uses dependency injection by default.
• Unified Web API + MVC pipeline.
• Lightweight and middleware-based request processing.

SP.NET Core 2.0.

• Each .cshtml file has an associated PageModel class (like a view +

controller combined).

• Best for simple UI-focused apps or CRUD pages.

✅ Use Razor Pages for:

• Simpler, page-focused apps

✅ Use MVC for:

• Complex, controller-based routing or large, structured apps

When to use Razor Pages instead of

MVC?

• Razor Pages is a page-based programming model introduced in

ASP.NET Core 2.0.

• Each .cshtml file has an associated PageModel class (like a view +

controller combined).

• Best for simple UI-focused apps or CRUD pages.

✅ Use Razor Pages for:

• Simpler, page-focused apps

✅ Use MVC for:

• Complex, controller-based routing or large, structured apps

• MVC Routing:
• Uses attribute routing or conventional routing.

Example:

endpoints.MapControllerRoute(

name: "default",

pattern: "{controller=Home}/{action=Index}/{id?}");

• Razor Pages Routing:
• Based on folder structure.
• URL /Products/Edit maps to

/Pages/Products/Edit.cshtml.

Answer: }"); Razor Pages Routing: Based on folder structure. URL /Products/Edit maps to /Pages/Products/Edit.cshtml.

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: view or JSON). View: .cshtml file that renders HTML. View Component: Reusable mini-views with logic (like partials but with code-behind).

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

• Controller: Handles HTTP requests.
• Action Method: A method in the controller that returns a result (like

a view or JSON).

• View: .cshtml file that renders HTML.
• View Component: Reusable mini-views with logic (like partials but

with code-behind).

Tag Helpers: Use HTML-like syntax. Easier to read/maintain.

<form asp-controller="Home" asp-action="Login"></form>

• HTML Helpers: C# methods used in Razor.

@Html.BeginForm("Login", "Home")

• ✅ Prefer Tag Helpers in modern ASP.NET Core apps.

ta cross requests No Preserved for 1 redirect only

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: Purpose ViewDa Current request No Pass data to views ViewBa Current request Yes ViewData wrapper (dynamic) TempD ata Across requests No Preserved for 1 redirect only

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: Automatically maps form values, query strings, route data to C# model properties. public IActionResult Submit(User user) { ... } Binds complex types and simple types out-of-the-box.

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: Decorate model properties: public class User { [Required] [EmailAddress] public string Email { get; set; } } Automatically validated during model binding. Use ModelState.IsValid to check.

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: IValidatableObject: public IEnumerable&lt;ValidationResult&gt; Validate(ValidationContext context) Custom Attribute: public class MyCustomAttribute : ValidationAttribute { public override bool IsValid(object value) { ... } }

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

• Layouts: Shared structure (e.g. header, footer) using

_Layout.cshtml.

• Partial Views: Reusable UI snippets (_LoginPartial.cshtml).
• View Components: Partial views with logic.

public class CartViewComponent : ViewComponent {
public IViewComponentResult Invoke() => View("Cart",

model);

}

Answer: Via ViewBag / ViewData / Model: return View(model); // Strongly typed ViewBag.Message = "Hello"; ViewData["Count"] = 5;

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: ActionFilter: Runs before/after action method. ResultFilter: Runs before/after view result. ExceptionFilter: Catches unhandled exceptions. Apply globally or via attributes. public class LogActionFilter : IActionFilter { ... }

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: Razor Pages use handler methods: public class IndexModel : PageModel { public void OnGet() { ... } public IActionResult OnPost() { ... } } You can use asp-page-handler="Update" for custom methods.

What interviewers expect

• A clear definition tied to ASP.NET Core in ASP.NET Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production ASP.NET Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in ASP.NET Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.