ResultToActionResult Extensions (MVC Support — v1.21.0)

Setup — required once per assembly:

// Any .cs file — typically Program.cs or AssemblyInfo.cs
[assembly: GenerateActionResultExtensions]

Without this attribute the source generator does not emit ToActionResult() / ToPostActionResult() / etc. for this assembly.

Convention-based HTTP mapping for ASP.NET MVC Controllers

// Convention-based — domain errors auto-map to correct HTTP status codes
[HttpGet]
public async Task<IActionResult> GetAll()
    => (await _service.GetAllUsersAsync()).ToActionResult();

[HttpPost]
public async Task<IActionResult> Create([FromBody] CreateUserRequest request)
    => (await _service.CreateUserAsync(request)).ToPostActionResult();

[HttpDelete("{id:int}")]
public async Task<IActionResult> Delete(int id)
    => (await _service.DeleteUserAsync(id)).ToDeleteActionResult();
    // NotFoundError → 404, ConflictError → 409, success → 204

// Explicit overload — escape hatch for full control
[HttpGet("{id:int}")]
public async Task<IActionResult> GetById(int id)
{
    return (await _service.GetUserAsync(id))
        .ToActionResult(
            onSuccess: user => Ok(user),
            onFailure: errors => NotFound(errors.First().Message));
}

Method	Success	Failure
ToActionResult<T>()	OkObjectResult (200)	Auto-mapped via HttpStatusCode tag
ToActionResult<T>(onSuccess, onFailure)	Custom	Custom
ToPostActionResult<T>()	CreatedResult (201)	Auto-mapped
ToPutActionResult<T>()	OkObjectResult (200)	Auto-mapped
ToPatchActionResult<T>()	OkObjectResult (200)	Auto-mapped
ToDeleteActionResult<T>()	NoContentResult (204)	Auto-mapped

MVC Error Auto-Mapping (MapErrorToActionResult)

Domain Error	HTTP	MVC Result Type
NotFoundError	404	NotFoundObjectResult
UnauthorizedError	401	UnauthorizedResult
ForbiddenError	403	ForbidResult
ConflictError	409	ConflictObjectResult
ValidationError	422	ObjectResult { StatusCode = 422 }
No tag / other	400	ObjectResult { StatusCode = 400 }