aspnet-minimal-api-openapi

Use the built-in OpenAPI support in .NET 9 with operation summaries, descriptions, and the WithName extension method to set operationIds. Add [Description] attributes to properties and parameters, and use document transformers for servers, tags, and security schemes.

Return TypedResults instead of Results for strongly-typed responses, and use Results<T1, T2> to represent multiple possible response types. This gives the OpenAPI generator accurate response schemas for each status code.

Yes, use the MapGroup() extension to group related endpoints under a common route prefix. You can apply endpoint filters to groups for cross-cutting concerns like validation or logging, and organize larger APIs with separate endpoint classes.

Use the ProblemDetailsService and StatusCodePages middleware to produce standard RFC 7807 problem details responses. Combine this with validation attributes like [Required] on your DTOs to enforce constraints consistently.

Use record types for immutable request and response objects, combined with C# 10+ features like nullable annotations and init-only properties. Records provide value-based equality and concise syntax ideal for DTOs.