.NET 10 Web API Development

Build production-ready ASP.NET Core Web APIs with .NET 10 using best practices from 2025.

Quick Start

Create a new Web API project:

scripts/new_api.sh <project_name> [output_directory]

Example:

scripts/new_api.sh ProductsApi
cd ProductsApi
dotnet build
dotnet run --project ProductsApi.Api

This creates:

• Solution with API and Test projects
• Controller-based Web API (.NET 10)
• xUnit test project with integration testing setup
• Proper folder structure (Controllers, Models, Services)
• .gitignore configured for .NET

Core Features

1. Project Scaffolding

Create New API Project:

scripts/new_api.sh MyApi ./projects

Generates:

• MyApi.Api - Main API project with controllers
• MyApi.Tests - xUnit test project with integration testing
• Solution file linking both projects
• Standard folder structure
• Test dependencies (FluentAssertions, WebApplicationFactory)

2. Add CRUD Entities

Generate Entity with Controller and Service:

scripts/add_entity.sh <entity_name> <project_path>

Example:

scripts/add_entity.sh Product ./MyApi
scripts/add_entity.sh Customer ./MyApi

Generates for each entity:

• Model class (Models/Product.cs)
• Service interface (Services/IProductService.cs)
• Service implementation (Services/ProductService.cs)
• CRUD controller (Controllers/ProductController.cs)
• Automatic service registration in DI container

API Endpoints Created:

GET    /api/Product        - Get all
GET    /api/Product/{id}   - Get by ID
POST   /api/Product        - Create
PUT    /api/Product/{id}   - Update
DELETE /api/Product/{id}   - Delete

3. Package Management

Add NuGet Packages:

scripts/add_package.sh <project_path> <package_name|preset>

Presets:

# Entity Framework with PostgreSQL
scripts/add_package.sh ./MyApi ef-postgres

# Entity Framework with SQL Server
scripts/add_package.sh ./MyApi ef-sqlserver

# JWT Authentication
scripts/add_package.sh ./MyApi auth

# FluentValidation
scripts/add_package.sh ./MyApi validation

# Individual package
scripts/add_package.sh ./MyApi Newtonsoft.Json

4. Docker Support

Generate Dockerfile and docker-compose:

scripts/generate_dockerfile.sh <project_path>

Example:

scripts/generate_dockerfile.sh ./MyApi

Generates:

• Multi-stage optimized Dockerfile
• docker-compose.yml with PostgreSQL
• .dockerignore
• Non-root user configuration
• Health check setup

Build and run:

docker-compose up -d
docker-compose logs -f api

.NET 10 Features

Built-in Features

OpenAPI 3.1 Support:

// Program.cs
builder.Services.AddOpenApi();

if (app.Environment.IsDevelopment())
{
    app.MapOpenApi(); // /openapi/v1.json
}

Automatic Minimal API Validation: DataAnnotations are automatically validated in .NET 10 for Minimal APIs and controllers.

Output Caching:

builder.Services.AddOutputCache();
app.UseOutputCache();

[OutputCache(Duration = 300)]
[HttpGet]
public async Task<IActionResult> GetAll()

Rate Limiting:

builder.Services.AddRateLimiter(options =>
{
    options.AddFixedWindowLimiter("api", config =>
    {
        config.PermitLimit = 100;
        config.Window = TimeSpan.FromMinutes(1);
    });
});

C# 14.0 Features

Use latest C# features:

• Primary constructors
• Collection expressions
• Required members
• Init-only properties

Development Workflows

Typical Development Flow

1. Create project:

   scripts/new_api.sh OrderService
   cd OrderService
   

2. Add entities:

   scripts/add_entity.sh Order .
   scripts/add_entity.sh OrderItem .
   

3. Add database:

   scripts/add_package.sh . ef-postgres
   

4. Build and run:

   dotnet build
   dotnet run --project OrderService.Api
   

5. Test:

   dotnet test
   

6. Dockerize:

   scripts/generate_dockerfile.sh .
   docker-compose up
   

Entity Framework Integration

After adding EF packages, configure DbContext:

// Data/ApplicationDbContext.cs
public class ApplicationDbContext : DbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options) { }

    public DbSet<Product> Products => Set<Product>();
}

// Program.cs
builder.Services.AddDbContext<ApplicationDbContext>(options =>
    options.UseNpgsql(builder.Configuration.GetConnectionString("DefaultConnection")));

// appsettings.json
{
  "ConnectionStrings": {
    "DefaultConnection": "Host=localhost;Database=mydb;Username=postgres;Password=postgres"
  }
}

Run migrations:

dotnet ef migrations add Initial --project MyApi.Api
dotnet ef database update --project MyApi.Api

Authentication Setup

After adding auth package:

// Program.cs
builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.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"]))
        };
    });

app.UseAuthentication();
app.UseAuthorization();

// Protect endpoints
[Authorize]
[HttpGet("admin")]
public IActionResult AdminOnly() => Ok("Admin data");

Best Practices

Controller Pattern

Generated controllers follow best practices:

[ApiController]
[Route("api/[controller]")]
public class ProductController : ControllerBase
{
    private readonly IProductService _service;
    private readonly ILogger<ProductController> _logger;

    // Constructor injection
    public ProductController(
        IProductService service,
        ILogger<ProductController> logger)
    {
        _service = service;
        _logger = logger;
    }

    // Documented endpoints
    /// <summary>
    /// Get all products
    /// </summary>
    [HttpGet]
    [ProducesResponseType(StatusCodes.Status200OK)]
    public async Task<ActionResult<IEnumerable<Product>>> GetAll()

    // Proper status codes
    [HttpPost]
    [ProducesResponseType(StatusCodes.Status201Created)]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    public async Task<ActionResult<Product>> Create(Product entity)
    {
        var created = await _service.CreateAsync(entity);
        return CreatedAtAction(nameof(GetById), new { id = created.Id }, created);
    }
}

Service Layer Pattern

// Interface
public interface IProductService
{
    Task<IEnumerable<Product>> GetAllAsync();
    Task<Product?> GetByIdAsync(int id);
    Task<Product> CreateAsync(Product entity);
    Task<Product?> UpdateAsync(int id, Product entity);
    Task<bool> DeleteAsync(int id);
}

// Implementation with business logic
public class ProductService : IProductService
{
    // In-memory for demo, replace with repository/DbContext
    private readonly List<Product> _entities = new();

    public async Task<Product> CreateAsync(Product entity)
    {
        entity.Id = _nextId++;
        entity.CreatedAt = DateTime.UtcNow;
        _entities.Add(entity);
        return entity;
    }
}

Testing

Generated test projects include integration testing setup:

public class ProductsEndpointTests : IClassFixture<WebApplicationFactory<Program>>
{
    private readonly HttpClient _client;

    public ProductsEndpointTests(WebApplicationFactory<Program> factory)
    {
        _client = factory.CreateClient();
    }

    [Fact]
    public async Task GetAll_ReturnsSuccessStatusCode()
    {
        var response = await _client.GetAsync("/api/products");
        response.EnsureSuccessStatusCode();
    }
}

Run tests:

dotnet test
dotnet test --logger "console;verbosity=detailed"

References

For detailed guidance, see:

API Best Practices

references/api_best_practices.md - Comprehensive guide covering:

• RESTful API design
• HTTP status codes
• Error handling patterns
• Validation strategies
• Authentication & authorization
• Dependency injection
• Logging best practices
• Performance optimization
• OpenAPI documentation

Testing Patterns

references/testing_patterns.md - Testing guide including:

• xUnit fundamentals
• Unit testing with Moq
• Integration testing with WebApplicationFactory
• Test data builders
• FluentAssertions usage
• Common testing patterns

Common Packages

references/common_packages.md - NuGet package guide for:

• Database providers (EF Core, Dapper)
• Authentication (JWT, Identity)
• Validation (FluentValidation)
• Testing tools (xUnit, Moq, FluentAssertions)
• Logging (Serilog)
• Utilities (AutoMapper, MediatR, Polly)

Common Scenarios

Scenario 1: New CRUD API

# Create project
scripts/new_api.sh InventoryApi

# Add entities
scripts/add_entity.sh Product ./InventoryApi
scripts/add_entity.sh Category ./InventoryApi

# Add database
scripts/add_package.sh ./InventoryApi ef-postgres

# Run
cd InventoryApi
dotnet run --project InventoryApi.Api

Scenario 2: Microservice with Docker

# Create and setup
scripts/new_api.sh OrderService
scripts/add_entity.sh Order ./OrderService
scripts/add_package.sh ./OrderService ef-postgres
scripts/generate_dockerfile.sh ./OrderService

# Deploy
cd OrderService
docker-compose up -d

Scenario 3: Authenticated API

scripts/new_api.sh SecureApi
scripts/add_entity.sh User ./SecureApi
scripts/add_package.sh ./SecureApi auth
scripts/add_package.sh ./SecureApi validation

Troubleshooting

.NET SDK Not Found

Ensure .NET 10 SDK is installed:

dotnet --version  # Should be 10.x

Install from: https://dotnet.microsoft.com/download/dotnet/10.0

Port Already in Use

Change port in Properties/launchSettings.json or use environment variable:

ASPNETCORE_HTTP_PORTS=5001 dotnet run --project MyApi.Api

Docker Build Fails

Ensure Docker daemon is running:

docker ps

Check Dockerfile paths match project structure.

EF Migrations Fail

Ensure connection string is correct and database is accessible:

dotnet ef database update --verbose --project MyApi.Api

Integration with Other Skills

Works well with:

• postgres-query - Query databases created by your API
• postgres-backup-restore - Restore test data for development
• ruby-rails - Interop with Rails backends

Summary

This skill provides:

✅ Rapid project scaffolding ✅ CRUD entity generation ✅ NuGet package management ✅ Docker containerization ✅ .NET 10 best practices ✅ Testing setup included ✅ Production-ready code structure ✅ Comprehensive documentation

Start building modern Web APIs with .NET 10 today!