Overview

Haitch.Results provides Result, Result<T>, and Result<T, TError> types for representing operation outcomes without exceptions. It includes a structured Error model with categorised error types.

Targets .NET 10+.

Installation

.NET CLI

dotnet add package Haitch.Results

Package Reference

<PackageReference Include="Haitch.Results" Version="*" />

Quick example

using Haitch.Results;

Result<int> Parse(string input)
{
    if (int.TryParse(input, out var value))
        return value; // implicit conversion to success

    return Error.Validation("parse.failed", $"'{input}' is not a valid integer.");
}

var result = Parse("42");

var message = result.Match(
    onSuccess: v => $"Parsed: {v}",
    onFailure: e => $"Error: {e.Message}"
);

Core concepts

Result types represent success or failure:

Type	Description
Result	No value on success. Carries an Error on failure.
Result<T>	Carries a T on success, an Error on failure.
Result<T, TError>	Carries a T on success, a custom TError on failure.

Error is a record with a machine-readable Code, a human-readable Message, an ErrorType category, and optional Metadata.

ErrorType categorises errors: Failure, Validation, NotFound, Conflict, Unauthorized, Forbidden, Unexpected.

Implicit conversions

All generic result types support implicit conversion from both success values and errors, so you can return values or errors directly without calling factory methods.

Result<User> GetUser(int id)
{
    var user = db.Find(id);
    if (user is null)
        return Error.NotFound("user.not_found", $"No user with id {id}.");

    return user; // implicit Success
}