ResultPattern — Solution Overview

A modular, zero-exception result pattern library for .NET.
Represent operation outcomes without throwing exceptions — with built-in stack trace diagnostics, multi-error aggregation, and first-class HTTP Problem Details support.

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📦 Packages

Package	Description
ResultPattern	Core library — Result<T>, Error, Ensure, Combine
ResultPattern.Extension.MinimalAPI	Problem Details mapping for Minimal API endpoints
ResultPattern.Extension.MVC	Problem Details mapping for MVC & Web API controllers

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✨ Why ResultPattern?

Most result pattern libraries tell you what went wrong. This one also tells you where.

Every Error automatically captures a ResultStackTrace at the call site via compiler attributes — no manual tracking, no extra setup.

[NotFound Error] Restaurant with id '5' not found.
  at DeleteRestaurantCommandHandler.cs:line 14

Key Design Principles

• No exceptions for control flow — failures are values
• Full error aggregation — surface all violations at once
• Zero production leakage — stack traces omitted outside Development
• Implicit conversions — return values or errors naturally
• HTTP-ready — each Error carries an HttpStatusCode

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📦 ResultPattern

Install in any project that produces or consumes results.

dotnet add package ResultPattern

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Result<TValue>

Represents either a success value or a collection of errors — never both.

Member	Type	Description
Value	TValue	Safe only when IsSuccess is true
Errors	IReadOnlyList<Error>?	null on success
IsSuccess	bool	true when no errors

Implicit Conversions

Result<int> fromValue  = 42;
Result<int> fromError  = Error.NotFound("Item not found.");
Result<int> fromErrors = new List<Error>
{
    Error.Validation("Name required."),
    Error.Validation("Email required.")
};

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Success

A readonly record struct used for operations without a return value.

return Result.Success;

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Error — With Built-in Stack Trace

Immutable record representing categorized failure.

Property	Type	Description
Code	string	Machine-readable category
Description	string	Human-readable message
StatusCode	HttpStatusCode	HTTP status mapping
StackTrace.FileName	string	Source file
StackTrace.MemberName	string	Method name
StackTrace.LineNumber	int	Line number

StackTrace is [JsonIgnore] and never appears in API responses.

Error Factories

Method	HTTP Status
Error.Failure(...)	500
Error.Unexpected(...)	500
Error.Validation(...)	422
Error.Conflict(...)	409
Error.NotFound(...)	404
Error.Unauthorized(...)	401
Error.Forbidden(...)	403

return Error.NotFound($"Restaurant with id '{id}' not found.");
return Error.Forbidden("You do not have permission.");
return Error.Validation("Invalid email.");

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🆕 Result.Ensure<T> — Multi-Rule Validation

Validates a single value against multiple rules.

Each rule is:

(Predicate<T> predicate, Error error)

Behavior

• Predicate returning true = PASS
• Predicate returning false = FAIL (error collected)
• All rules always run
• No short-circuiting

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Example — Primitive Validation

var nameValidation = Result.Ensure(name,
    (n => !string.IsNullOrEmpty(n), Error.Validation("Name cannot be null or empty.")),
    (n => n?.Length >= 3, Error.Validation("Name must be at least 3 characters."))
);

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Example — Domain Rule Validation

var ensureResult = Result.Ensure(restaurant,
    (
        r => restaurantAuthorization.Authorize(r, ResourceOperation.Delete),
        Error.Forbidden($"You are not the owner of restaurant '{request.Id}'.")
    ),
    (
        r => !r.HasActiveOrders,
        Error.Conflict($"Restaurant '{request.Id}' has active orders and cannot be deleted.")
    )
);

if (!ensureResult.IsSuccess)
    return ensureResult.Errors!.ToList();

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🆕 Result.Combine

Aggregates multiple pre-computed results into one.

• All succeed → Result.Success
• Any fail → returns all collected errors
• No short-circuiting

public static Result<User> Create(string name, string email)
{
    var nameValidation = Result.Ensure(name,
        (n => !string.IsNullOrEmpty(n), Error.Validation("Name required.")),
        (n => n?.Length >= 3, Error.Validation("Name too short."))
    );

    var emailValidation = Result.Ensure(email,
        (e => !string.IsNullOrEmpty(e), Error.Validation("Email required.")),
        (e => e?.Length >= 3, Error.Validation("Email too short.")),
        (e => e?.Contains("@"), Error.Validation("Invalid email."))
    );

    var combined = Result.Combine([nameValidation, emailValidation]);

    if (!combined.IsSuccess)
        return combined.Errors!.ToList();

    return new User(name, email);
}

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Match<TNextValue>

Pattern matching without if statements.

return result.Match(
    onValue: _ => Results.NoContent(),
    onError: errors => Results.UnprocessableEntity(errors)
);

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Ensure vs Combine

	Ensure	Combine
Input	Value + rules	Multiple results
Evaluation	All rules run	All results evaluated
Short-circuit	❌ No	❌ No
Aggregates errors	✅ Yes	✅ Yes
Use case	Entity/field validation	Merge validations

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📦 ResultPattern.Extension.MinimalAPI

dotnet add package ResultPattern.Extension.MinimalAPI

Register

builder.Services.AddResponseHelper();

Usage

app.MapDelete("/restaurants/{id}", async (
    Guid id,
    ISender sender,
    ResponseHelper responseHelper,
    CancellationToken ct) =>
{
    var result = await sender.Send(new DeleteRestaurantCommand(id), ct);

    return result.Match(
        _ => Results.NoContent(),
        responseHelper.ToProblemResult);
});

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📦 ResultPattern.Extension.MVC

dotnet add package ResultPattern.Extension.MVC

Register

builder.Services.AddResponseHelper();

Usage

[HttpDelete("{id:guid}")]
public async Task<IActionResult> Delete(Guid id, CancellationToken ct)
{
    var result = await _sender.Send(new DeleteRestaurantCommand(id), ct);

    return result.Match(
        _ => NoContent(),
        _responseHelper.ToProblemResult);
}

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Environment-Aware Diagnostics

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

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Extension Package Comparison

	MinimalAPI	MVC
Return type	IResult	ActionResult
Factory	Results.Problem	ProblemDetailsFactory
HttpContext source	Endpoint parameter	IHttpContextAccessor
Use in	app.Map*	ControllerBase
Stack trace in Dev	✅	✅

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