dotnet-webapi

ASP.NET Core Web API

Produce well-structured ASP.NET Core Web API endpoints with proper HTTP semantics, OpenAPI documentation, and error handling.

When to Use

Use this skill when working on ASP.NET Core HTTP APIs, including:

• adding or modifying Web API endpoints implemented with controllers or minimal APIs;
• wiring up OpenAPI/Swagger metadata and endpoint documentation;
• defining request/response DTOs and consistent HTTP status code behavior;
• adding .http files or similar request-based API testing artifacts;
• configuring centralized API error handling middleware or exception mapping.

When Not to Use

Do not use this skill for:

• general C# coding style or non-API refactoring;
• EF Core data modeling or query optimization work; use optimizing-ef-core-queries;
• frontend, Razor, or Blazor UI changes;
• gRPC services;
• SignalR hubs or real-time messaging flows.

Inputs / prerequisites

Before applying this skill, gather the project context needed to match the existing API style and wiring:

• the ASP.NET Core entry point, typically Program.cs;
• any existing controllers, especially classes inheriting ControllerBase or using [ApiController];
• any existing minimal API registrations such as app.MapGet, app.MapPost, app.MapPut, or app.MapDelete;
• related DTO, model, validation, and error-handling types already used by the project;
• available build, run, and test commands so changes can be verified.

If the user asks for a new endpoint, inspect the current project structure first so the implementation follows the established conventions rather than mixing styles.

Workflow

Step 1: Determine the API style

Scan the project for existing endpoint patterns before writing any code.

1. Search for classes inheriting ControllerBase or decorated with [ApiController].
2. Search Program.cs or endpoint files for app.MapGet, app.MapPost, etc.
3. If the project already uses controllers, continue with controllers.
4. If the project already uses minimal APIs, continue with minimal APIs.
5. If neither exists (new project), default to minimal APIs unless the user explicitly requests controllers.