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ASP.NET Core Quick Reference

Minimal APIs​

// Basic endpoint
app.MapGet("/api/products", () => Results.Ok(products));

// With parameters
app.MapGet("/api/products/{id:int}", (int id) => { });

// With DI
app.MapGet("/api/products", (IProductService service) => service.GetAll());

// Route groups
var api = app.MapGroup("/api/products")
    .WithTags("Products")
    .RequireAuthorization();

Dependency Injection​

// Registration
builder.Services.AddTransient<IService, Service>();  // New each time
builder.Services.AddScoped<IService, Service>();     // One per request
builder.Services.AddSingleton<IService, Service>();  // One for app lifetime

// Usage
public class MyController
{
    private readonly IService _service;

    public MyController(IService service)
    {
        _service = service;
    }
}

Middleware Pipeline​

app.UseHttpsRedirection();    // 1. HTTPS redirect
app.UseRouting();              // 2. Match endpoint
app.UseCors();                 // 3. CORS
app.UseAuthentication();       // 4. Who are you?
app.UseAuthorization();        // 5. What can you do?
app.UseRateLimiter();          // 6. Rate limit
app.MapControllers();          // 7. Execute

Configuration​

// appsettings.json
{
  "ApiSettings": {
    "ApiKey": "secret",
    "Timeout": 30
  }
}

// Registration
builder.Services.Configure<ApiSettings>(
    builder.Configuration.GetSection("ApiSettings"));

// Usage
public class MyService
{
    private readonly ApiSettings _settings;

    public MyService(IOptions<ApiSettings> options)
    {
        _settings = options.Value;
    }
}

HTTP Status Codes​

CodeUse
200OK (GET, PUT, PATCH)
201Created (POST)
204No Content (DELETE)
400Bad Request
401Unauthorized
403Forbidden
404Not Found
500Server Error

Endpoint Filters​

app.MapPost("/api/products", CreateProduct)
    .AddEndpointFilter(async (context, next) =>
    {
        // Validation logic
        return await next(context);
    });

Rate Limiting​

builder.Services.AddRateLimiter(options =>
{
    options.AddFixedWindowLimiter("fixed", opt =>
    {
        opt.Window = TimeSpan.FromSeconds(10);
        opt.PermitLimit = 5;
    });
});

app.UseRateLimiter();
app.MapGet("/api/products", GetAll).RequireRateLimiting("fixed");

Model Validation​

public class Product
{
    [Required]
    [StringLength(100)]
    public string Name { get; set; }

    [Range(0.01, 10000)]
    public decimal Price { get; set; }
}

Controller Actions​

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    [HttpGet]
    public IActionResult GetAll() => Ok(products);

    [HttpGet("{id}")]
    public IActionResult Get(int id) => Ok(product);

    [HttpPost]
    public IActionResult Create(Product product)
        => CreatedAtAction(nameof(Get), new { id }, product);
}

Resources​