A Simple Analogy

Imagine building a LEGO city with just the essential blocks. Minimal APIs let you create powerful web endpoints using only what you need—no extra pieces, no heavy frameworks. As you get advanced, you learn to build bridges, tunnels, and skyscrapers with those same simple blocks.

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What Are Minimal APIs?

Minimal APIs are a way to build HTTP APIs in ASP.NET Core using the least amount of ceremony. You define endpoints directly in your Program.cs or a module, skipping controllers and attributes. Advanced usage means you can still add authentication, validation, OpenAPI docs, and more—just with less code.

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Why Use Minimal APIs?

• Simplicity: Write less code, get more done.
• Performance: Fewer layers, faster execution.
• Flexibility: Add only the features you need.
• Rapid prototyping: Great for microservices, serverless, and quick experiments.

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Advanced Patterns & Features

1. Endpoint Grouping & Modularization

Organize endpoints for clarity and reuse:

var users = app.MapGroup("/users");
users.MapGet("/", GetAllUsers);
users.MapPost("/", CreateUser);

2. Dependency Injection

Inject services directly into handlers:

app.MapGet("/weather", (IWeatherService svc) => svc.GetForecast());

3. Request Validation

Use libraries like FluentValidation or custom logic:

app.MapPost("/orders", async (OrderDto order, IValidator<OrderDto> validator) => {
    var result = await validator.ValidateAsync(order);
    if (!result.IsValid) return Results.BadRequest(result.Errors);
    // ...
});

4. Authentication & Authorization

Protect endpoints with policies:

app.MapGet("/admin", [Authorize] () => "Secret stuff");

Or use endpoint configuration:

app.MapGet("/profile", GetProfile).RequireAuthorization();

5. OpenAPI/Swagger Integration

Auto-generate docs with minimal setup:

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

app.UseSwagger();
app.UseSwaggerUI();

6. Custom Middleware

Add logic before/after endpoints:

app.Use(async (ctx, next) => {
    // Logging, metrics, etc.
    await next();
});

7. Response Formatting

Return JSON, custom status codes, or files:

app.MapGet("/download", () => Results.File("report.pdf"));

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Practical Examples

• Build a RESTful API for a todo app
• Create a webhook receiver for Stripe or GitHub
• Serve static files and dynamic endpoints together
• Implement JWT authentication for secure APIs
• Add input validation for user-submitted data

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Real-World Use Cases

• Microservices: Lightweight, focused APIs for each service
• Serverless: Azure Functions or AWS Lambda with minimal code
• Rapid prototyping: MVPs and hackathon projects
• IoT: Fast endpoints for device communication
• Internal tools: Dashboards, admin panels, automation scripts

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Best Practices

• Group related endpoints for clarity
• Use dependency injection for testability
• Validate all incoming data
• Secure sensitive endpoints with authentication
• Document your API with OpenAPI/Swagger
• Handle errors gracefully (Results.Problem, Results.BadRequest)
• Keep business logic out of endpoint handlers—use services

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Related Concepts to Explore

• ASP.NET Core Routing
• Middleware pipeline
• Dependency Injection in .NET
• OpenAPI/Swagger
• Authentication & Authorization (JWT, OAuth)
• Model validation (FluentValidation)
• RESTful API design
• gRPC and SignalR (for real-time and binary APIs)
• Serverless architectures
• Testing Minimal APIs (unit/integration)

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Summary

Minimal APIs let you build fast, focused web endpoints with just the essentials. Advanced patterns unlock modularity, security, validation, and documentation—so you can scale from a tiny prototype to a robust production service, all with minimal code.