tranhieutt .NET Backend Development Patterns
C#/.NET patterns for production-grade APIs, MCP servers, and enterprise backends.
API Structure (Minimal API + Controllers)
```csharp // Program.cs - Minimal API var builder = WebApplication.CreateBuilder(args); builder.Services.AddDbContext(o => o.UseNpgsql(connStr)); builder.Services.AddScoped<IOrderService, OrderService>();
var app = builder.Build(); app.MapGet("/orders/{id}", async (int id, IOrderService svc) => await svc.GetByIdAsync(id) is { } order ? Results.Ok(order) : Results.NotFound()); ```
Dependency Injection Patterns
```csharp // Register services builder.Services.AddScoped<IPaymentService, StripePaymentService>(); builder.Services.AddSingleton<ICacheService, RedisCacheService>(); builder.Services.AddHttpClient<IApiClient, ExternalApiClient>(client => { client.BaseAddress = new Uri("https://api.external.com"); }); ```
Lifetime guide: Singleton (stateless/cache), Scoped (per-request), Transient (stateless utility).
Entity Framework Core
```csharp // DbContext with conventions public class AppDbContext : DbContext { public DbSet Orders => Set(); protected override void OnModelCreating(ModelBuilder builder) { builder.Entity().HasIndex(o => o.UserId); builder.Entity().Property(o => o.Total).HasPrecision(18, 2); } } ```
Performance tips:
- Use
.AsNoTracking()for read-only queries - Avoid N+1 with
.Include()or projection - Use compiled queries for hot paths
Middleware Pipeline
```csharp app.UseMiddleware(); app.UseAuthentication(); app.UseAuthorization(); app.UseRateLimiter(); app.MapControllers(); ```
Error Handling
```csharp // Global exception handler app.UseExceptionHandler(err => err.Run(async context => { var exception = context.Features.Get()?.Error; var (status, message) = exception switch { NotFoundException => (404, exception.Message), UnauthorizedAccessException => (403, "Forbidden"), _ => (500, "Internal server error") }; context.Response.StatusCode = status; await context.Response.WriteAsJsonAsync(new { error = message }); })); ```
Configuration (IOptions pattern)
```csharp builder.Services.Configure( builder.Configuration.GetSection("Stripe"));
// Usage public class PaymentService(IOptions opts) { private readonly string _key = opts.Value.SecretKey; } ```
Testing
```csharp // Integration test with WebApplicationFactory public class OrderApiTests : IClassFixture<WebApplicationFactory> { private readonly HttpClient _client; [Fact] public async Task GetOrder_ReturnsOk() { var response = await _client.GetAsync("/orders/1"); response.StatusCode.Should().Be(HttpStatusCode.OK); } } ```
Related Skills
backend-architect— architecture decisionsdatabase-architect— schema designdrizzle-orm-expert— Node.js ORM alternative