Interview Q&A

Short answer: Anti-Forgery Tokens Protects against CSRF attacks In Razor: <form method="post"> @Html.AntiForgeryToken() </form> In API: use services.AddAntiforgery(), validate via [ValidateAntiForgeryToken]. 1⃣

Real-world example (ShopNest)

ShopNest’s product edit form posts to an MVC action. Model binding fills a ProductEditVm; the action validates and redisplay the view on errors.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Creating REST APIs in ASP.NET Core is straightforward using controllers or minimal PIs.

Explain a bit more

Example: Traditional Controller-Based API dotnet new webapi -n MyApi Program.cs: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); pp.MapControllers(); pp.Run(); Controller: [ApiController] [Route("api/[controller]")] public class ProductsController : ControllerBase { [HttpGet] public IActionResult GetAll() => Ok(new[] { "Laptop", "Phone" }); } ✅ You get RESTful endpoints automatically (GET /api/products). {

Example code

if (!ModelState.IsValid)
return BadRequest(ModelState);
return CreatedAtAction(nameof(CreateOrder), new { id = 1 }, order); }
} 📦 3. How does content negotiation work? Content negotiation allows clients to request responses in a specific format (JSON, XML, etc.) using the Accept header. SP.NET Core automatically picks the best formatter: GET /api/products ccept: application/json Response → JSON GET /api/products ccept: application/xml Response → XML (if XML formatter is added) Enable XML Support: builder.Services.AddControllers() .AddXmlSerializerFormatters(); 🧭 4. How to handle versioning in APIs? You can version APIs to maintain backward compatibility using the Microsoft.AspNetCore.Mvc.Versioning package. Install: dotnet add package Microsoft.AspNetCore.Mvc.Versioning Configure: builder.Services.AddApiVersioning(options => {
options.DefaultApiVersion = new ApiVersion(1, 0);
options.AssumeDefaultVersionWhenUnspecified = true;
{ [HttpGet] public IActionResult Get() => Ok("Version 1");
} ⚠ 5. What is ProblemDetails? ProblemDetails is a standardized JSON structure for API error responses (RFC 7807). Example Output: { "type": " "title": "Resource not found", "status": 404, "detail": "Product with ID 5 was not found" } Usage: return NotFound(new ProblemDetails
{ Title = "Product not found", Status = StatusCodes.Status404NotFound, Detail = "The product ID 5 does not exist." }); 🚦 6. How to return custom HTTP status codes? You can use built-in helpers from ControllerBase: Method Status Code Ok() 200 Created() / CreatedAtAction() 201 NoContent() 204 BadRequest() 400 Unauthorized() 401 NotFound() 404 StatusCode(500) Custom Example: return StatusCode(503, "Service temporarily unavailable"); 📄 7. How to implement pagination in APIs? Pagination helps manage large datasets efficiently. Example: [HttpGet] public IActionResult GetProducts([FromQuery] int page = 1, [FromQuery] int size = 10) {
var data = _context.Products .Skip((page - 1) * size) .Take(size) .ToList(); var totalCount = _context.Products.Count(); Response.Headers.Add("X-Total-Count", totalCount.ToString()); return Ok(data);
} ✅ Supports GET /api/products?page=2&size=5. 🔐 8. How to secure APIs with JWT tokens? Use JWT (JSON Web Token) authentication for stateless security. Setup in Program.cs: builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationS cheme) .AddJwtBearer(options => { options.TokenValidationParameters = new TokenValidationParameters { ValidateIssuer = true, ValidIssuer = " ValidateAudience = true, ValidAudience = " IssuerSigningKey = new SymmetricSecurityKey( Encoding.UTF8.GetBytes("super-secret-key")) }; }); Then protect controllers: [Authorize] [ApiController] [Route("api/[controller]")] public class OrdersController : ControllerBase
{ [HttpGet] public IActionResult GetOrders() => Ok("Secure data");
} ⚡ 9. What is rate limiting in .NET 8? .NET 8 introduces built-in rate limiting middleware to control API request rates. Example: builder.Services.AddRateLimiter(options => { options.AddFixedWindowLimiter("fixed", opt => {
opt.PermitLimit = 5; // 5 requests
opt.Window = TimeSpan.FromSeconds(10); // per 10 seconds
var exception = context.Features.Get<IExceptionHandlerFeature>()?.Error; return Results.Problem(title: "Unexpected error", detail: exception?.Message); }); Or write a custom middleware for consistent error formatting. 🧾 11. How to use Swagger / OpenAPI? Swagger generates interactive API documentation automatically. Setup: builder.Services.AddEndpointsApiExplorer(); builder.Services.AddSwaggerGen(); var app = builder.Build();
if (app.Environment.IsDevelopment())
{ pp.UseSwagger(); pp.UseSwaggerUI(); } Run → Navigate to ✅ You can test endpoints directly from the browser. 🧰 12. What is NSwag or Swashbuckle? Both tools generate OpenAPI/Swagger documentation, but with slight differences: Tool Description Swashbuckle.AspNetCor Most common; adds Swagger UI, docs, and JSON schema NSwag Adds extra features like client SDK generation for C#/TypeScript Example (NSwag client generation): nswag openapi2csclient /input: /output:Client.cs 📤 13. How to upload files via Web API? Use IFormFile for file uploads. Controller Example: [HttpPost("upload")] public async Task<IActionResult> UploadFile(IFormFile file)
{
if (file == null || file.Length == 0)
return BadRequest("No file uploaded.");
var path = Path.Combine("wwwroot/uploads", file.FileName);
using var stream = new FileStream(path, FileMode.Create); wait file.CopyToAsync(stream); return Ok(new { file.FileName, file.Length });
} Client sends multipart/form-data POST requests. 🌐 14. How to implement CORS? CORS (Cross-Origin Resource Sharing) allows requests from other domains (e.g., frontend pps). Enable in Program.cs: builder.Services.AddCors(options => { options.AddPolicy("AllowReactApp", policy => policy.WithOrigins(" .AllowAnyHeader() .AllowAnyMethod()); }); var app = builder.Build(); pp.UseCors("AllowReactApp"); ✅ Now your React or Angular frontend can call your API safely. 🚀 15. What’s new in .NET 8 Minimal APIs? Minimal APIs let you build lightweight REST endpoints without controllers — great for microservices. Example: var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.UseAuthentication(); pp.UseAuthorization(); pp.UseAuthentication(); pp.UseAuthorization(); pp.UseAuthentication(); pp.UseAuthorization(); pp.UseAuthentication(); pp.UseAuthorization();

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ASP.NET Core Identity is a membership system that manages users, passwords, roles, claims, and authentication.

Explain a bit more

It provides: User registration & login Password hashing Role & claims management Two-factor authentication Cookie & token-based authentication You can scaffold Identity to get ready-to-use pages for login, registration, and password reset. ASP.NET Core Identity is a membership system that manages users, passwords, roles, claims, and authentication. It provides: User registration & login Password hashing Role & claims management Two-factor authentication Cookie & token-based authentication

Example code

You can scaffold Identity to get ready-to-use pages for login, registration, and password reset. ASP.NET Core Identity is a membership system that manages users, passwords, roles, claims, and authentication. It provides: User registration & login Password hashing Role & claims management Two-factor authentication Cookie & token-based authentication Example: You can scaffold Identity to get ready-to-use pages for login, registration, and password reset. ⚙ 2. How do you configure Identity in ASP.NET Core? Add Identity services in Program.cs: builder.Services.AddDbContext<AppDbContext>(options => options.UseSqlServer(builder.Configuration.GetConnectionString("Defa ultConnection"))); builder.Services.AddIdentity<ApplicationUser, IdentityRole>() .AddEntityFrameworkStores<AppDbContext>() .AddDefaultTokenProviders(); ASP.NET Core Identity is a membership system that manages users, passwords, roles, claims, and authentication. It provides: User registration & login Password hashing Role & claims management Two-factor authentication Cookie & token-based authentication Example: You can scaffold Identity to get ready-to-use pages for login, registration, and password reset. ⚙ 2. How do you configure Identity in ASP.NET Core? Add Identity services in Program.cs: builder.Services.AddDbContext<AppDbContext>(options => options.UseSqlServer(builder.Configuration.GetConnectionString("Defa ultConnection"))); builder.Services.AddIdentity<ApplicationUser, IdentityRole>() .AddEntityFrameworkStores<AppDbContext>() .AddDefaultTokenProviders();

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: If you change appsettings.json and configuration reload is enabled, IOptionsMonitor picks up the new value without restarting the app. Entity Framework Core

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: MVC stands for Model–View–Controller, a design pattern that separates application logic into three layers: Model – Represents the data and business logic (e.g., Product, Customer, Order). View – The UI or presentation layer that displays data (Razor views). {

Example code

public IActionResult Details(int id)
{
var product = _service.GetById(id);
return View(product);
}
} Notes: Action methods cannot be private or static. They respond to routes like /Product/Details/5. 🎯 6. What are Action Results? An Action Result represents the response returned to the client — view, JSON, redirect, file, etc. SP.NET Core provides many result types: ViewResult JsonResult RedirectResult FileResult ContentResult StatusCodeResult 🔍 7. Difference between ViewResult, JsonResult, and ContentResult. Type Used For Example ViewResult Returns an HTML view return View("Details", model); JsonResult Returns JSON data return Json(model); ContentResul Returns plain text or custom content return Content("Hello World"); IActionResult is an interface that represents the result of an action method. It allows flexibility — you can return any kind of result (view, JSON, redirect, etc.) from the same method. Example: public IActionResult Index()
{
if (!User.Identity.IsAuthenticated)
return RedirectToAction("Login");
return View();
} 🧠 9. How does model binding work? Model binding automatically maps data from the HTTP request (query string, route, body, form) to method parameters or model objects. Example: public IActionResult Save(Product model)
{ // model properties are automatically filled _service.Add(model); return RedirectToAction("Index");
}
{ [Required] public string Name { get; set; } [Range(1, 10000)] public decimal Price { get; set; }
} In a controller: if (!ModelState.IsValid)
return View(model);

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: SP.NET MVC 5? ASP.NET Core is a cross-platform, open-source framework for building modern web pplications, APIs, and microservices. It’s a complete rewrite of the old ASP.NET framework, designed to be lightweight, modular, and cloud-ready. Key Differences: Feature ASP.NET MVC 5 ASP.NET Core Platform Windows only Cross-platform (Windows, macOS,… Linux)……… Hosting IIS only Kestrel, IIS, Nginx, Apache, self-hosting…

Explain a bit more

Configuration web.config (XML) appsettings.json (JSON-based) Dependency Injection Third-party libraries Built-in DI container Modularity Monolithic Modular via NuGet packages Example: In ASP.NET MVC 5, you’d deploy only to IIS on Windows. {

Example code

public void ConfigureServices(IServiceCollection services)
{ services.AddControllers(); }
public void Configure(IApplicationBuilder app)
{ pp.UseRouting(); pp.UseEndpoints(endpoints => endpoints.MapControllers());
}
} 🧭 6. Explain the purpose of Program.cs in .NET 6+. In .NET 6+, Startup.cs and Program.cs merged into one minimal host configuration file. It sets up the web host, configuration, logging, and middleware pipeline. Example: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); pp.MapControllers(); pp.Run(); It’s simpler, faster, and easier to read. Minimal APIs are a lightweight way to build small HTTP APIs without controllers or ttributes. Perfect for microservices. Example: var app = WebApplication.Create(args);
{ [HttpGet("{id}")] public IActionResult Get(int id) => Ok($"Product {id}");
} 🧩 11. What is Endpoint Routing? Endpoint routing separates route matching from execution. It lets middleware (like authentication) know which endpoint will be executed before it runs. Example: pp.UseRouting(); pp.UseAuthorization(); pp.UseEndpoints(endpoints => endpoints.MapControllers()); 🔄 12. Explain the role of middleware in ASP.NET Core. Middleware are components that handle requests and responses in a pipeline. Each can: Process requests Call the next middleware Or short-circuit the pipeline Example: logging middleware that runs before all others: pp.Use(async (context, next) => { Console.WriteLine("Request: " + context.Request.Path); wait next(); }); 🕒 13. What is the order of middleware execution? Middleware execute in the order they’re added in Program.cs. Response flows in reverse order back up the chain. Tip: Authentication must come before Authorization. UseRouting must come before UseEndpoints. 🧩 14. How to create custom middleware? Example: public class RequestLoggingMiddleware
{
private readonly RequestDelegate _next;
public RequestLoggingMiddleware(RequestDelegate next) => _next = next; public async Task Invoke(HttpContext context)
{ Console.WriteLine($"Request for: {context.Request.Path}"); wait _next(context); }
} Register it: pp.UseMiddleware<RequestLoggingMiddleware>(); 🧱 15. What is the difference between middleware and filters? Feature Middleware Filter Scope Entire app Controller/action level Runs on Every request MVC actions only Example Authentication, logging Validation, exception filters ⚒ 16. Explain the IApplicationBuilder interface. IApplicationBuilder builds the middleware pipeline. You use it in Startup.Configure() or Program.cs to add middleware via Use, Run, nd Map. 🔀 17. Difference between Use, Run, and Map in middleware. Metho Description Example Use Adds middleware that can call the next component. pp.UseMiddleware<Logging>(); Run Terminates the pipeline — no next middleware. pp.Run(async c => await c.Response.WriteAsync("End")); Map Branches pipeline based on request path. pp.Map("/admin", a => .Run(...)); 🏗 18. What are Hosting Models in ASP.NET Core (In-process vs Out-of-process)? Model Description Performance In-process App runs inside IIS worker process (w3wp.exe). Faster (single process) Out-of-proces IIS acts as reverse proxy to Kestrel. Slight overhead Example: For Windows servers, in-process gives best performance. For cross-platform Docker, use out-of-process. 🌍 19. Explain Web Host vs Generic Host. Host Type Used For Example Web Host Web apps (ASP.NET Core ≤ 2.2) WebHost.CreateDefaultBui lder() Generic Host ny app: web, worker, console (≥ 3.0) Host.CreateDefaultBuilde r() Generic Host unifies background tasks, APIs, and services in one model. ⚙ 20. How does configuration binding work in SP.NET Core? ASP.NET Core can automatically bind configuration from: appsettings.json Environment variables Command-line arguments Example: // appsettings.json { "AppSettings": { "SiteName": "MyShop", "Version": "1.0" }
} // POCO public class AppSettings
{
public string SiteName { get; set; }
public string Version { get; set; }
} // Program.cs builder.Services.Configure<AppSettings>( builder.Configuration.GetSection("AppSettings")); You can inject IOptions<AppSettings> anywhere. MVC Architecture & Controllers

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: dotnet publish -c Release

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Install package: dotnet add package Microsoft.Extensions.Caching.StackExchangeRedis

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Caching improves performance by storing frequently used data in memory or external storage to reduce database or API calls. SP.NET Core provides:

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Creating REST APIs in ASP.NET Core is straightforward using controllers or minimal APIs.

Explain a bit more

Traditional Controller-Based API dotnet new webapi -n MyApi Program.cs: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); app.MapControllers(); app.Run(); Controller: [ApiController] [Route("api/[controller]")] public class ProductsController : ControllerBase [HttpGet] public IActionResult GetAll() => Ok(new[] { "Laptop", "Phone" }); ✅ You get RESTful endpoints automatically (GET /api/products). Creating REST APIs in ASP.NET Core is straightforward using controllers or minimal APIs.

Example code

Traditional Controller-Based API dotnet new webapi -n MyApi Program.cs: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); app.MapControllers(); app.Run(); Controller: [ApiController] [Route("api/[controller]")] public class ProductsController : ControllerBase [HttpGet] public IActionResult GetAll() => Ok(new[] { "Laptop", "Phone" }); ✅ You get RESTful endpoints automatically (GET /api/products). Creating REST APIs in ASP.NET Core is straightforward using controllers or minimal APIs. Example: Traditional Controller-Based API dotnet new webapi -n MyApi Program.cs: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); app.MapControllers(); app.Run(); Controller: [ApiController] [Route("api/[controller]")] public class ProductsController : ControllerBase [HttpGet] public IActionResult GetAll() => Ok(new[] { "Laptop", "Phone" }); ✅ You get RESTful endpoints automatically (GET /api/products). Creating REST APIs in ASP.NET Core is straightforward using controllers or minimal APIs. Example: Traditional Controller-Based API dotnet new webapi -n MyApi Program.cs: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); app.MapControllers(); app.Run(); Controller: [ApiController] [Route("api/[controller]")] public class ProductsController : ControllerBase [HttpGet] public IActionResult GetAll() => Ok(new[] { "Laptop", "Phone" }); ✅ You get RESTful endpoints automatically (GET /api/products). 🧱 2. What is the [ApiController] attribute? [ApiController] simplifies building APIs by adding smart defaults: Automatic model validation → 400 Bad Request on invalid models Automatic [FromBody], [FromQuery], etc. inference Follow : ProblemDetails JSON response for errors Example: [ApiController] [Route("api/[controller]")] public class OrdersController : ControllerBase [HttpPost] public IActionResult CreateOrder(Order order) if (!ModelState.IsValid) return BadRequest(ModelState); return CreatedAtAction(nameof(CreateOrder), new { id = 1 }, order); 📦 3. How does content negotiation work? Content negotiation allows clients to request responses in a specific format (JSON, XML, etc.) using the Accept header. ASP.NET Core automatically picks the best formatter: GET /api/products Accept: application/json Response → JSON GET /api/products Accept: application/xml Response → XML (if XML formatter is added) Follow : Enable XML Support: builder.Services.AddControllers() .AddXmlSerializerFormatters(); 🧭 4. How to handle versioning in APIs? You can version APIs to maintain backward compatibility using the Microsoft.AspNetCore.Mvc.Versioning package. Install: dotnet add package Microsoft.AspNetCore.Mvc.Versioning Configure: builder.Services.AddApiVersioning(options => options.DefaultApiVersion = new ApiVersion(1, 0); options.AssumeDefaultVersionWhenUnspecified = true; options.ReportApiVersions = true; }); Use in controllers: [ApiVersion("1.0")] [Route("api/v{version:apiVersion}/products")] [ApiController] public class ProductsV1Controller : ControllerBase [HttpGet] public IActionResult Get() => Ok("Version 1"); ⚠ 5. What is ProblemDetails? Follow : ProblemDetails is a standardized JSON structure for API error responses (RFC 7807). Example Output: "type": " "title": "Resource not found", "status": 404, "detail": "Product with ID 5 was not found" Usage: return NotFound(new ProblemDetails Title = "Product not found", Status = StatusCodes.Status404NotFound, Detail = "The product ID 5 does not exist." }); 🚦 6. How to return custom HTTP status codes? You can use built-in helpers from ControllerBase: Method Status Code Ok() 200 Created() / CreatedAtAction() 201 NoContent() 204 BadRequest() 400 Unauthorized() 401 Follow : NotFound() 404 StatusCode(500) Custom Example: return StatusCode(503, "Service temporarily unavailable"); 📄 7. How to implement pagination in APIs? Pagination helps manage large datasets efficiently. Example: [HttpGet] public IActionResult GetProducts([FromQuery] int page = 1, [FromQuery] int size = 10) var data = _context.Products .Skip((page - 1) * size) .Take(size) .ToList(); var totalCount = _context.Products.Count(); Response.Headers.Add("X-Total-Count", totalCount.ToString()); return Ok(data); ✅ Supports GET /api/products?page=2&size=5. 🔐 8. How to secure APIs with JWT tokens? Use JWT (JSON Web Token) authentication for stateless security. Follow : Setup in Program.cs: builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationS cheme) .AddJwtBearer(options => options.TokenValidationParameters = new TokenValidationParameters ValidateIssuer = true, ValidIssuer = " ValidateAudience = true, ValidAudience = " IssuerSigningKey = new SymmetricSecurityKey( Encoding.UTF8.GetBytes("super-secret-key")) }); Then protect controllers: [Authorize] [ApiController] [Route("api/[controller]")] public class OrdersController : ControllerBase [HttpGet] public IActionResult GetOrders() => Ok("Secure data"); ⚡ 9. What is rate limiting in .NET 8? .NET 8 introduces built-in rate limiting middleware to control API request rates. Example: builder.Services.AddRateLimiter(options => Follow : options.AddFixedWindowLimiter("fixed", opt => opt.PermitLimit = 5; // 5 requests opt.Window = TimeSpan.FromSeconds(10); // per 10 seconds opt.QueueLimit = 0; }); }); var app = builder.Build(); app.UseRateLimiter(); app.MapGet("/api/data", () => "Hello") .RequireRateLimiting("fixed"); ✅ Prevents abuse or DDoS attacks by throttling requests. 🚨 10. How do you handle exceptions in APIs? Use global exception handling middleware instead of try/catch everywhere. Example: app.UseExceptionHandler("/error"); app.Map("/error", (HttpContext context) => var exception = context.Features.Get<IExceptionHandlerFeature>()?.Error; return Results.Problem(title: "Unexpected error", detail: exception?.Message); }); Or write a custom middleware for consistent error formatting. Follow : 🧾 11. How to use Swagger / OpenAPI? Swagger generates interactive API documentation automatically. Setup: builder.Services.AddEndpointsApiExplorer(); builder.Services.AddSwaggerGen(); var app = builder.Build(); if (app.Environment.IsDevelopment()) app.UseSwagger(); app.UseSwaggerUI(); Run → Navigate to ✅ You can test endpoints directly from the browser. 🧰 12. What is NSwag or Swashbuckle? Both tools generate OpenAPI/Swagger documentation, but with slight differences: Tool Description Swashbuckle.AspNetCor Most common; adds Swagger UI, docs, and JSON schema NSwag Adds extra features like client SDK generation for C#/TypeScript Example (NSwag client generation): Follow : nswag openapi2csclient /input: /output:Client.cs 📤 13. How to upload files via Web API? Use IFormFile for file uploads. Controller Example: [HttpPost("upload")] public async Task<IActionResult> UploadFile(IFormFile file) if (file == null || file.Length == 0) return BadRequest("No file uploaded."); var path = Path.Combine("wwwroot/uploads", file.FileName); using var stream = new FileStream(path, FileMode.Create); await file.CopyToAsync(stream); return Ok(new { file.FileName, file.Length }); Client sends multipart/form-data POST requests. 🌐 14. How to implement CORS? CORS (Cross-Origin Resource Sharing) allows requests from other domains (e.g., frontend apps). Enable in Program.cs: builder.Services.AddCors(options => Follow : options.AddPolicy("AllowReactApp", policy => policy.WithOrigins(" .AllowAnyHeader() .AllowAnyMethod()); }); var app = builder.Build(); app.UseCors("AllowReactApp"); ✅ Now your React or Angular frontend can call your API safely. 🚀 15. What’s new in .NET 8 Minimal APIs? Minimal APIs let you build lightweight REST endpoints without controllers — great for microservices. Example: var builder = WebApplication.CreateBuilder(args); var app = builder.Build(); app.MapGet("/products", () => new[] { "Phone", "Tablet" }); app.MapPost("/products", (Product product) => Results.Created($"/products/{product.Id}", product)); app.Run(); New in .NET 8: Route groups for grouping endpoints Input validation with [Validate] attributes Enhanced OpenAPI (Swagger) support Rate limiting, Authorization, and Filters integration Follow : Typed results for consistent HTTP responses ✅ Minimal APIs now rival traditional controllers for small, fast APIs. Performance & Caching

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ASP.NET Core configuration is flexible, layered, and environment-aware.

Explain a bit more

It reads settings from multiple sources (JSON files, environment variables, command-line rgs, etc.) and merges them into a single configuration object (IConfiguration).

Example code

In Program.cs: var builder = WebApplication.CreateBuilder(args); // Access configuration var appName = builder.Configuration["AppSettings:Name"]; SP.NET Core automatically loads:

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationS cheme) .AddJwtBearer(options => { options.TokenValidationParameters = new TokenValidationParameters { ValidateIssuer = true, ValidateAudience = true, ValidateLifetime = true, ValidateIssuerSigningKey = true, ValidIssuer = " ValidAudience = " IssuerSigningKey = new… SymmetricSecurityKey(……… Encoding.UTF8.GetBytes("super-secret-key-123")) }; });…

Explain a bit more

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationS cheme) .AddJwtBearer(options => { options.TokenValidationParameters = new TokenValidationParameters { ValidateIssuer = true, ValidateAudience = true, ValidateLifetime = true, ValidateIssuerSigningKey = true, ValidIssuer = " ValidAudience = " IssuerSigningKey = new SymmetricSecurityKey( Encoding.UTF8.GetBytes("super-secret-key-123")) }; }); builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationS cheme) .AddJwtBearer(options => { options.TokenValidationParameters = new TokenValidationParameters { ValidateIssuer = true, ValidateAudience = true,…

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build();…

Explain a bit more

app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization();

Example code

var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization(); var app = builder.Build(); app.UseAuthentication(); app.UseAuthorization();

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: options.UseLazyLoadingProxies().UseSqlServer(...); options.UseLazyLoadingProxies().UseSqlServer(...); options.UseLazyLoadingProxies().UseSqlServer(...); options.UseLazyLoadingProxies().UseSqlServer(...);

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Entity Framework Core (EF Core) is a modern, lightweight, cross-platform ORM (Object Relational Mapper) from Microsoft. It allows .NET developers to work with databases using .NET objects, without writing most SQL manually. {

Example code

public AppDbContext(DbContextOptions<AppDbContext> options) : base(options) { } public DbSet<Product> Products { get; set; }
} 🧱 4. What are Migrations? Migrations allow you to evolve your database schema as your models change, without losing existing data. Commands: dotnet ef migrations add InitialCreate dotnet ef database update This creates a Migrations folder with code that applies schema changes automatically. 🧩 5. What is the OnModelCreating method used for? OnModelCreating is where you configure entity behavior and relationships using the Fluent API. Example: protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<Product>() .Property(p => p.Name) .HasMaxLength(100) .IsRequired(); modelBuilder.Entity<Order>() .HasMany(o => o.Items) .WithOne(i => i.Order) .HasForeignKey(i => i.OrderId);
} Use it for constraints, relationships, indexes, seeding, and more. 💤 6. How do you enable Lazy Loading in EF Core? Lazy loading means related entities are loaded automatically when accessed. To enable it: Install the package: dotnet add package Microsoft.EntityFrameworkCore.Proxies

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ASP.NET Core is a cross-platform, open-source framework for building modern web applications, APIs, and microservices.

Explain a bit more

It’s a complete rewrite of the old ASP.NET framework, designed to be lightweight, modular, and cloud-ready. In ASP.NET MVC 5, you’d deploy only to IIS on Windows. In ASP.NET Core, the same app can run on a Linux server using Nginx + Kestrel — perfect for Docker or cloud environments. ⚙ 2. Explain the request-processing pipeline in ASP.NET Core. ASP.NET Core handles incoming requests through a middleware pipeline. Each middleware can process, modify, or short-circuit requests before they reach the endpoint. Flow

Example code

Request → Middleware 1 (Logging) → Middleware 2 (Authentication) → Middleware 3 (Routing) → Controller / Endpoint → Response → Back through pipeline Follow : Example: If you log requests, check authentication, and handle static files — they execute in the order you add them in Program.cs. app.UseStaticFiles(); app.UseRouting(); app.UseAuthentication(); app.UseAuthorization(); app.MapControllers(); 🧱 3. What is Kestrel? Kestrel is a cross-platform web server built into ASP.NET Core. It’s fast, lightweight, and serves as the default web server. You can run it standalone or behind a reverse proxy like IIS or Nginx. Real Example: When you run dotnet run, your app listens on — that’s Kestrel serving your app. 🖥 4. What is the role of IIS when hosting ASP.NET Core apps? IIS acts as a reverse proxy. It forwards incoming HTTP requests to the Kestrel server running your ASP.NET Core app. This setup provides: Process management (auto-restart) Port sharing (multiple sites) Windows authentication Logging and monitoring Follow : In short: IIS → forwards → Kestrel → runs the app. 🚀 5. What is the Startup class used for? The Startup class defines how your app configures services (DI, authentication, etc.) and sets up middleware (routing, static files, error pages, etc.). Example: public class Startup public void ConfigureServices(IServiceCollection services) services.AddControllers(); public void Configure(IApplicationBuilder app) app.UseRouting(); app.UseEndpoints(endpoints => endpoints.MapControllers()); 🧭 6. Explain the purpose of Program.cs in .NET 6+. In .NET 6+, Startup.cs and Program.cs merged into one minimal host configuration file. It sets up the web host, configuration, logging, and middleware pipeline. Example: var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); Follow : app.MapControllers(); app.Run(); It’s simpler, faster, and easier to read. 🔹 7. What is a Minimal API? Minimal APIs are a lightweight way to build small HTTP APIs without controllers or attributes. Perfect for microservices. Example: var app = WebApplication.Create(args); app.MapGet("/hello", () => "Hello World!"); app.Run(); This single file can run a full REST endpoint. 🧰 8. What is the WebApplicationBuilder in .NET 6/7/8? WebApplicationBuilder simplifies creating and configuring a web host. It combines: IHostBuilder WebHostBuilder Configuration Services Example: var builder = WebApplication.CreateBuilder(args); Follow : builder.Services.AddDbContext<AppDbContext>(); builder.Services.AddControllers(); Then you call builder.Build() to create the WebApplication. 🛣 9. How does routing work in ASP.NET Core MVC? Routing maps incoming URLs to controllers and actions. ASP.NET Core uses Endpoint Routing to decide which route matches a request. Example: app.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}"); If the user visits /product/details/5, it maps to: ProductController → Details(int id = 5). 🏷 10. Difference between Conventional and Attribute Routing. Type Definition Example Conventional Routing Routes defined in Program.cs or Startup.cs. {controller=Home}/{action=Ind ex}/{id?} Attribute Routing Routes defined with attributes on controller actions. [Route("api/products/{id}")] Example: [Route("api/[controller]")] Follow : public class ProductsController : ControllerBase [HttpGet("{id}")] public IActionResult Get(int id) => Ok($"Product {id}"); 🧩 11. What is Endpoint Routing? Endpoint routing separates route matching from execution. It lets middleware (like authentication) know which endpoint will be executed before it runs. Example: app.UseRouting(); app.UseAuthorization(); app.UseEndpoints(endpoints => endpoints.MapControllers()); 🔄 12. Explain the role of middleware in ASP.NET Core. Middleware are components that handle requests and responses in a pipeline. Each can: Process requests Call the next middleware Or short-circuit the pipeline Example: A logging middleware that runs before all others: app.Use(async (context, next) => Console.WriteLine("Request: " + context.Request.Path); Follow : await next(); }); 🕒 13. What is the order of middleware execution? Middleware execute in the order they’re added in Program.cs. Response flows in reverse order back up the chain. Tip: Authentication must come before Authorization. UseRouting must come before UseEndpoints. 🧩 14. How to create custom middleware? Example: public class RequestLoggingMiddleware private readonly RequestDelegate _next; public RequestLoggingMiddleware(RequestDelegate next) => _next = next; public async Task Invoke(HttpContext context) Console.WriteLine($"Request for: {context.Request.Path}"); await _next(context); Register it: app.UseMiddleware<RequestLoggingMiddleware>(); Follow : 🧱 15. What is the difference between middleware and filters? Feature Middleware Filter Scope Entire app Controller/action level Runs on Every request MVC actions only Example Authentication, logging Validation, exception filters ⚒ 16. Explain the IApplicationBuilder interface. IApplicationBuilder builds the middleware pipeline. You use it in Startup.Configure() or Program.cs to add middleware via Use, Run, and Map. 🔀 17. Difference between Use, Run, and Map in middleware. Metho Description Example Use Adds middleware that can call the next component. app.UseMiddleware<Logging>(); Run Terminates the pipeline — no next middleware. app.Run(async c => await c.Response.WriteAsync("End")); Map Branches pipeline based on request path. app.Map("/admin", a => a.Run(...)); Follow : 🏗 18. What are Hosting Models in ASP.NET Core (In-process vs Out-of-process)? Model Description Performance In-process App runs inside IIS worker process (w3wp.exe). Faster (single process) Out-of-proces IIS acts as reverse proxy to Kestrel. Slight overhead Example: For Windows servers, in-process gives best performance. For cross-platform Docker, use out-of-process. 🌍 19. Explain Web Host vs Generic Host. Host Type Used For Example Web Host Web apps (ASP.NET Core ≤ 2.2) WebHost.CreateDefaultBui lder() Generic Host Any app: web, worker, console (≥ 3.0) Host.CreateDefaultBuilde r() Generic Host unifies background tasks, APIs, and services in one model. ⚙ 20. How does configuration binding work in ASP.NET Core? ASP.NET Core can automatically bind configuration from: appsettings.json Environment variables Follow : Command-line arguments Example: // appsettings.json "AppSettings": { "SiteName": "MyShop", "Version": "1.0" // POCO public class AppSettings public string SiteName { get; set; } public string Version { get; set; } // Program.cs builder.Services.Configure<AppSettings>( builder.Configuration.GetSection("AppSettings")); You can inject IOptions<AppSettings> anywhere. MVC Architecture & Controllers

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Middleware vs Filters vs Handlers Concept When It Runs Scope Example Middleware Before/after request Global Logging, authentication Filters Around controller/action Controller/action Authorization, validation Handlers Authentication/Authorization Global or endpoint JWT handler, Cookie auth 1⃣

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: How ASP.NET Core Handles gRPC gRPC uses HTTP/2, binary serialization (Protobuf), and strongly typed contracts. Add gRPC service: builder.Services.AddGrpc(); app.MapGrpcService<MyGrpcService>(); Clients can call server methods over HTTP/2 for high-performance RPC. Use Cases: Microservices, real-time streaming, low-latency APIs.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: dotnet publish -c Release -o C:\inetpub\wwwroot\MyApp

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: builder.Services.AddStackExchangeRedisCache(options => { options.Configuration = "localhost:6379"; }); builder.Services.AddStackExchangeRedisCache(options => { options.Configuration = "localhost:6379"; }); builder.Services.AddStackExchangeRedisCache(options => { options.Configuration = "localhost:6379"; });… builder.Services.AddStackExchangeRedisCache(options => { options.Configuration = "localhost:6379"; });

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Environment variables are great for overriding settings at deployment time (especially in Docker or Azure). Example: set ASPNETCORE_ENVIRONMENT=Production set ConnectionStrings__Default="Server=mydb;Database=App;User=sa;Passwor d=123" Notice the double underscores __ for nested keys. {

Example code

private readonly IWebHostEnvironment _env;
public HomeController(IWebHostEnvironment env)
{
_env = env;
}
public IActionResult Index()
{
if (_env.IsDevelopment())
return Content("Running in Development mode");
return Content($"Environment: {_env.EnvironmentName}");
}
} You can also access it in Program.cs: if (builder.Environment.IsProduction())
{ // Configure production services } 🧾 8. How to use different appsettings.json files? ASP.NET Core supports environment-specific JSON files. Example structure: ppsettings.json ppsettings.Development.json ppsettings.Staging.json ppsettings.Production.json Program.cs: builder.Configuration .AddJsonFile("appsettings.json") .AddJsonFile($"appsettings.{builder.Environment.EnvironmentName}.jso n", optional: true); t runtime, only the file matching the current environment will override base settings. Example: ppsettings.json { "AppName": "MyApp", "LogLevel": "Information" } ppsettings.Production.json { "LogLevel": "Error" } Result in Production → LogLevel = Error. 🔄 9. How to reload configuration dynamically? You can make JSON configuration files auto-reload when changed. Example: builder.Configuration.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true); If you update appsettings.json, the new values are reflected automatically in your app without restarting. You can subscribe to changes using IOptionsMonitor (see below). 📦 10. How to bind configuration to POCO classes? You can map sections of your configuration directly to C# classes (POCOs). Example: ppsettings.json { "AppSettings": { "SiteName": "TechStore", "PageSize": 20, "EnableCache": true }
} Create a POCO: public class AppSettings
{
public string SiteName { get; set; }
public int PageSize { get; set; }
public bool EnableCache { get; set; }
} Bind configuration: builder.Services.Configure<AppSettings>( builder.Configuration.GetSection("AppSettings")); Inject it into a controller: public class HomeController : Controller
{
private readonly AppSettings _settings;
public HomeController(IOptions<AppSettings> options)
{
_settings = options.Value;
}
public IActionResult Index()
{
return Content($"Welcome to {_settings.SiteName}!");
}
} You can also use IOptionsSnapshot for per-request reload or IOptionsMonitor for live updates. Web APIs & REST

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: [Authorize] [ApiController] [Route("api/[controller]")] public class OrdersController : ControllerBase { [HttpGet] public IActionResult GetOrders() => Ok("Secured Orders"); } [Authorize] [ApiController] [Route("api/[controller]")] public class OrdersController : ControllerBase { [HttpGet] public IActionResult GetOrders() =>… Ok("Secured Orders"); }… [Authorize] [ApiController] [Route("api/[controller]")] public…

Explain a bit more

class OrdersController : ControllerBase { [HttpGet] public IActionResult GetOrders() => Ok("Secured Orders"); } [Authorize] [ApiController] [Route("api/[controller]")] public class OrdersController : ControllerBase { [HttpGet] public IActionResult GetOrders() =>… Ok("Secured Orders"); }

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get;…

Explain a bit more

set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } }

Example code

public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } } public class ApplicationUser : IdentityUser { public string FullName { get; set; } }

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use compiled queries for frequently executed queries.? is a common interview topic in ASP.NET Core MVC. Give a clear definition, then one concrete example.

Real-world example (ShopNest)

ShopNest admin screens use MVC: controller loads data, Razor view renders HTML, Tag Helpers build forms safely.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.