ASP.NET Core integration for Monad.NET. IActionResult extensions and middleware for Option, Result, Validation, and Try types.
Get Started
$ dotnet add package Monad.NET.AspNetCoreReadme
Monad.NET.AspNetCore
ASP.NET Core integration for Monad.NET.
Installation
dotnet add package Monad.NET.AspNetCore
Features
- IActionResult Extensions - Convert monad types directly to HTTP responses
- Exception Middleware - Catch exceptions and return Result-style responses
- ValidationProblemDetails Support - Automatic conversion to RFC 7807 format
Quick Start
IActionResult Extensions
Convert monad types directly to HTTP responses in your controllers:
using Monad.NET;
using Monad.NET.AspNetCore;
[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
private readonly IUserService _userService;
// Option → 200 OK or 404 Not Found
[HttpGet("{id}")]
public IActionResult GetUser(int id)
{
return _userService.FindUser(id)
.ToActionResult("User not found");
}
// Result → 200 OK or error status
[HttpPost]
public IActionResult CreateUser(CreateUserRequest request)
{
return _userService.CreateUser(request)
.ToActionResult(StatusCodes.Status400BadRequest);
}
// Validation → 200 OK or 422 with validation errors
[HttpPut("{id}")]
public IActionResult UpdateUser(int id, UpdateUserRequest request)
{
return ValidateRequest(request)
.ToValidationProblemResult();
}
// Async support
[HttpGet("{id}/profile")]
public async Task<IActionResult> GetUserProfile(int id)
{
return await _userService.GetUserProfileAsync(id)
.ToActionResultAsync();
}
}
Custom Response Mapping
// Custom mapping for Result
return result.ToActionResult(
onOk: user => CreatedAtAction(nameof(GetUser), new { id = user.Id }, user),
onErr: error => error switch
{
UserError.NotFound => NotFound(),
UserError.Duplicate => Conflict(error),
_ => BadRequest(error)
}
);
// Custom mapping for Option
return option.ToActionResult(
onSome: user => Ok(new { User = user, Timestamp = DateTime.UtcNow }),
onNone: () => NotFound(new { Message = "User not found" })
);
Exception Handling Middleware
Catch unhandled exceptions and return consistent Result-style responses:
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
// Add early in the pipeline
app.UseResultExceptionHandler(options =>
{
options.IncludeExceptionDetails = app.Environment.IsDevelopment();
options.IncludeStackTrace = app.Environment.IsDevelopment();
});
app.MapControllers();
app.Run();
Response format:
{
"isOk": false,
"error": {
"type": "InvalidOperationException",
"message": "Something went wrong"
}
}
ValidationProblemDetails Support
Convert validation errors to RFC 7807 format:
// Simple string errors
var validation = Validation<User, string>.Error(
new[] { "Name is required", "Email is invalid" }
);
return validation.ToValidationProblemResult("user");
// Keyed errors (field-specific)
var validation = Validation<User, KeyValuePair<string, string>>.Error(
new[]
{
KeyValuePair.Create("name", "Name is required"),
KeyValuePair.Create("email", "Email is invalid")
}
);
return validation.ToValidationProblemResult();
Response:
{
"title": "Validation failed",
"status": 422,
"errors": {
"name": ["Name is required"],
"email": ["Email is invalid"]
}
}
Available Extensions
Option Extensions
| Method | Description |
|---|---|
ToActionResult() | Some → 200 OK, None → 404 |
ToActionResult(message) | None → 404 with message |
ToActionResult(onSome, onNone) | Custom mapping |
ToActionResultWithProblemDetails() | None → ProblemDetails |
ToActionResultAsync() | Async version |
Result Extensions
| Method | Description |
|---|---|
ToActionResult(errorCode) | Ok → 200, Err → specified code |
ToActionResult(onOk, onErr) | Custom mapping |
ToActionResultOrNotFound() | Err → 404 |
ToCreatedResult(location) | Ok → 201 Created |
ToNoContentResult() | Ok → 204 No Content |
ToActionResultWithProblemDetails() | Err → ProblemDetails |
ToActionResultAsync() | Async versions |
Validation Extensions
| Method | Description |
|---|---|
ToActionResult() | Valid → 200, Invalid → 422 |
ToActionResult(onValid, onInvalid) | Custom mapping |
ToValidationProblemResult() | Invalid → ValidationProblemDetails |
ToCreatedResult(location) | Valid → 201 |
ToActionResultAsync() | Async versions |
Try Extensions
| Method | Description |
|---|---|
ToActionResult(includeDetails) | Success → 200, Failure → 500 |
ToActionResult(onSuccess, onFailure) | Custom mapping |
ToActionResultWithProblemDetails() | Failure → ProblemDetails |
ToActionResultAsync() | Async versions |
Requirements
- .NET 6.0 or later
- Monad.NET (automatically referenced)
License
MIT — Free for commercial and personal use.
Author: Behrang Mohseni