ASP.NET Core Minimal APIs: REST APIs Without Controllers

Minimal APIs, introduced in .NET 6, offer a streamlined way to build REST APIs without controller classes, routing attributes, or separate action method declarations. All endpoints are defined directly in Program.cs using MapGet, MapPost, MapPut, and MapDelete.

Key advantages: Less boilerplate, ideal for microservices and simple APIs, native dependency injection via lambda parameters, built-in OpenAPI/Swagger support, and strong performance.

The pattern: Register services in builder.Services, then map routes using app.Map*() methods. Lambda parameters are automatically resolved from the DI container, route values, query strings, or request body based on their source attributes.

Use Minimal APIs for small microservices, prototypes, and APIs with a limited number of endpoints. For larger APIs requiring complex filtering policies, action filters, and extensive attribute-based configuration, the traditional controller approach remains better organized.

For PHP developers exploring C#: Minimal APIs feel like registering routes in Symfony's RoutingConfigurator but with inline handlers — familiar territory.