Hesham.ResultPattern.Extension.MVC 1.1.2

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.

📦 Installation

dotnet add package ResultPattern.Extension.MVC

Requires: ResultPattern core package.

🚀 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.

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:

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
        }
      }
    ]
  }
}

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.

Environment-Aware Diagnostics

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

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);
    }
}

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:

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