ResultPattern.Extension.MVC

MVC & Web API response helpers for ResultPattern.
Maps Result<TValue> and List<Error> directly to standards-compliant HTTP Problem Details ActionResult responses — powered by ASP.NET Core's built-in ProblemDetailsFactory.

This package works with any class that inherits ControllerBase — including [ApiController] Web API controllers and traditional MVC controllers alike.

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📦 Installation

dotnet add package ResultPattern.Extension.MVC

Requires: ResultPattern core package.

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🚀 Quick Start

1. Register Services

builder.Services.AddResponseHelper();

2. Inject and Use in Controllers

[ApiController] [Route("api/[controller]")] public class BasketController : ControllerBase { private readonly ISender _sender; private readonly ResponseHelper _responseHelper; public BasketController(ISender sender, ResponseHelper responseHelper) { _sender = sender; _responseHelper = responseHelper; } [HttpGet("{userName}")] public async Task<IActionResult> GetBasket(string userName, CancellationToken ct) { var query = new GetBasketQuery(userName); Result<GetBasketResult> result = await _sender.Send(query, ct); return result.Match( val => Ok(val.Adapt<GetBasketResponse>()), _responseHelper.ToProblemResult); } }

ResponseHelper is registered as a scoped service and uses IHttpContextAccessor internally — inject it into any controller that needs result-to-response mapping.

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ResponseHelper

The core service exposed by this package. It takes a List<Error> and produces an ActionResult shaped as an RFC 7807 Problem Details response, using ASP.NET Core's ProblemDetailsFactory for full framework compatibility.

ToProblemResult(List<Error> errors)

The main entry point. Inspects the error list and delegates to the appropriate response builder:

Condition	Response Type	Status Code
All errors are 422 Unprocessable Entity	ValidationProblemDetails	422
Mixed or single non-validation error	ProblemDetails	Error's own HttpStatusCode
Null or empty error list	Generic ProblemDetails	500

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Response Shapes

Validation Errors — 422 Unprocessable Entity

Triggered when all errors in the list carry a 422 status code (i.e. all created via Error.Validation(...)).
All descriptions are collected, deduplicated, and added to ModelStateDictionary under the "errors" key — fully compatible with ASP.NET Core's standard validation response shape.

{ "title": "Validation", "status": 422, "detail": "One or more validation errors occurred.", "errors": { "errors": [ "Name cannot be null or empty.", "Name cannot be less than 3 characters.", "Invalid email address." ] } }

In Development, each error's full stack trace is appended under extensions.stackTraces:

{ "title": "Validation", "status": 422, "detail": "One or more validation errors occurred.", "errors": { "errors": [ "Name cannot be null or empty.", "Invalid email address." ] }, "extensions": { "stackTraces": [ { "description": "Name cannot be null or empty.", "stackTrace": { "memberName": "Create", "fileName": "User.cs", "lineNumber": 12 } }, { "description": "Invalid email address.", "stackTrace": { "memberName": "Create", "fileName": "User.cs", "lineNumber": 18 } } ] } }

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Single / Mixed Errors — Problem Details

Triggered when errors are not all 422 — e.g. 404, 403, 409, or 500.
The first error in the list drives the response status and title.

{ "title": "NotFound", "status": 404, "detail": "Restaurant with id '5' not found." }

In Development, the error's stack trace is appended under extensions.stackTrace:

{ "title": "NotFound", "status": 404, "detail": "Restaurant with id '5' not found.", "extensions": { "stackTrace": { "memberName": "Handle", "fileName": "DeleteRestaurantCommandHandler.cs", "lineNumber": 14 } } }

Stack traces are never exposed in Production. IHostEnvironment is checked internally — no configuration required.

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Environment-Aware Diagnostics

ResponseHelper automatically adjusts its response detail based on the current environment:

Field	Development	Production
extensions.stackTrace	✅ Included	❌ Omitted
extensions.stackTraces	✅ Included	❌ Omitted
Error descriptions	✅ Included	✅ Included
HTTP status codes	✅ Included	✅ Included

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Full Controller Example

A complete Web API controller using ResultPattern and ResponseHelper across multiple endpoints:

[ApiController] [Route("api/[controller]")] public class RestaurantsController : ControllerBase { private readonly ISender _sender; private readonly ResponseHelper _responseHelper; public RestaurantsController(ISender sender, ResponseHelper responseHelper) { _sender = sender; _responseHelper = responseHelper; } [HttpDelete("{id:guid}")] public async Task<IActionResult> Delete(Guid id, CancellationToken ct) { var command = new DeleteRestaurantCommand(id); Result<Success> result = await _sender.Send(command, ct); return result.Match( _ => NoContent(), _responseHelper.ToProblemResult); } [HttpPost] public async Task<IActionResult> Create(CreateRestaurantRequest request, CancellationToken ct) { var command = new CreateRestaurantCommand(request.Name, request.Address); Result<RestaurantResponse> result = await _sender.Send(command, ct); return result.Match( restaurant => CreatedAtAction(nameof(GetById), new { id = restaurant.Id }, restaurant), _responseHelper.ToProblemResult); } [HttpGet("{id:guid}")] public async Task<IActionResult> GetById(Guid id, CancellationToken ct) { var query = new GetRestaurantByIdQuery(id); Result<RestaurantResponse> result = await _sender.Send(query, ct); return result.Match( restaurant => Ok(restaurant), _responseHelper.ToProblemResult); } }

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MVC & Web API vs Minimal API

Both extension packages expose an identical ResponseHelper API surface and produce the same Problem Details response shapes. Choose based on how your application is structured:

	ResultPattern.Extension.MVC	ResultPattern.Extension.MinimalAPI
Return type	ActionResult	IResult
Factory	ProblemDetailsFactory	Results.Problem / Results.ValidationProblem
HttpContext source	IHttpContextAccessor	Endpoint delegate parameter
Use in	ControllerBase subclasses (MVC & Web API)	app.Map* endpoint delegates
Stack trace in Dev	✅ Yes	✅ Yes

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Related Packages

Package	Purpose
ResultPattern	Core Result<T>, Error, Ensure, Combine
ResultPattern.Extension.MinimalAPI	HTTP Problem Details mapping for Minimal APIs
ResultPattern.Extension.MVC	This package — HTTP Problem Details mapping for MVC & Web API Controllers