.NET Full Stack Interview Questions in Gurgaon

decimal Shipping(Order o) => o switch { { Total: >= 1000 } => 0m, { Country: "IN", Weight: < 2 } => 49m, { Country: "IN" } => 99m, { Weight: > 20 } => throw new ArgumentException("Too heavy"), _ => 499m }; Property and relational patterns replace long if-else chains, and the compiler warns if cases are not exhaustive.

private static readonly SemaphoreSlim _gate = new(5); public async Task<string> CallAsync(string url) { await _gate.WaitAsync(); try { return await _http.GetStringAsync(url); } finally { _gate.Release(); } } var results = await Task.WhenAll(urls.Select(CallAsync)); SemaphoreSlim supports async waiting, unlike lock. The finally block guarantees the slot is released even when a call fails.

// run three independent calls in parallel var userTask = userApi.GetAsync(id); var ordersTask = orderApi.GetAsync(id); var walletTask = walletApi.GetAsync(id); await Task.WhenAll(userTask, ordersTask, walletTask); var dashboard = new Dashboard(userTask.Result, ordersTask.Result, walletTask.Result); // timeout using WhenAny var work = SlowCallAsync(); if (await Task.WhenAny(work, Task.Delay(2000)) != work) throw new TimeoutException(); WhenAll completes when all finish; WhenAny returns the first task to finish.

await using var tx = await db.Database.BeginTransactionAsync(); try { db.Orders.Add(order); await db.SaveChangesAsync(); var stock = await db.Stocks.SingleAsync(s => s.ProductId == order.ProductId); stock.Quantity -= order.Quantity; await db.SaveChangesAsync(); await tx.CommitAsync(); } catch { await tx.RollbackAsync(); throw; } A single SaveChanges is already transactional; explicit transactions are needed when you combine several saves or raw SQL into one unit.

// entity query with parameters (interpolation becomes SqlParameter) var orders = await db.Orders .FromSql($"SELECT * FROM Orders WHERE City = {city}") .Where(o => o.Total > 1000) .ToListAsync(); // non-entity results var totals = await db.Database .SqlQuery<decimal>($"SELECT SUM(Total) AS Value FROM Orders") .ToListAsync(); // stored procedure await db.Database.ExecuteSqlAsync($"EXEC usp_CloseMonth {month}"); Never build SQL by string concatenation; FromSqlRaw with concatenated input invites SQL injection.

public class FileLogger : IDisposable { private readonly StreamWriter _writer = new("log.txt"); public void Log(string msg) => _writer.WriteLine(msg); public void Dispose() => _writer.Dispose(); } // using declaration disposes at end of scope using var logger = new FileLogger(); logger.Log("Started"); Dispose releases unmanaged resources such as file handles and connections deterministically instead of waiting for the GC.

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme) .AddJwtBearer(o => { o.TokenValidationParameters = new TokenValidationParameters { ValidateIssuer = true, ValidateAudience = true, ValidateLifetime = true, ValidateIssuerSigningKey = true, ValidIssuer = builder.Configuration["Jwt:Issuer"], ValidAudience = builder.Configuration["Jwt:Audience"], IssuerSigningKey = new SymmetricSecurityKey( Encoding.UTF8.GetBytes(builder.Configuration["Jwt:Key"]!)) }; }); builder.Services.AddAuthorization(); app.UseAuthentication(); app.UseAuthorization(); Then protect endpoints with [Authorize] or [Authorize(Roles = "Admin")].

public class Product { public int Id { get; set; } public bool IsDeleted { get; set; } } protected override void OnModelCreating(ModelBuilder mb) { mb.Entity<Product>().HasQueryFilter(p => !p.IsDeleted); } public override Task<int> SaveChangesAsync(CancellationToken ct = default) { foreach (var e in ChangeTracker.Entries<Product>().Where(e => e.State == EntityState.Deleted)) { e.State = EntityState.Modified; e.Entity.IsDeleted = true; } return base.SaveChangesAsync(ct); } Every query now hides deleted rows automatically; use IgnoreQueryFilters() for admin screens.