Desfecho 1.1.1

Desfecho

A simple and lightweight Result pattern implementation for .NET.

dotnet add package Desfecho
dotnet add package Desfecho.AspNetCore

Why

Stop throwing exceptions for expected failures. Return a Result<TValue> instead — it's either a value or one or more Errors.

public Result<TodoItem> CompleteTodoItem(Guid id)
{
    var todoItem = _todoItems.Find(id);

    if (todoItem is null)
    {
        return Error.NotFound("TodoItem.NotFound", $"Todo item '{id}' was not found.");
    }

    todoItem.Complete();
    return todoItem;
}

var result = CompleteTodoItem(id);

var message = result.Match(
    todoItem => $"Completed '{todoItem.Title}'.",
    errors => errors[0].Description);

Result<TValue> converts implicitly from TValue, Error and List<Error>, so returning one is all you need — no wrapping, no new.

Errors

An Error is a Code, a Description, and a Type:

Error.Validation("TodoItem.Title", "Title is required.");
Error.Unauthorized("TodoItem.Unauthorized", "Authentication is required.");
Error.Forbidden("TodoItem.Forbidden", "You do not have access to this todo item.");
Error.NotFound("TodoItem.NotFound", "Todo item was not found.");
Error.Conflict("TodoItem.Conflict", "Todo item already exists.");

Type is one of Validation, Unauthorized, Forbidden, NotFound or Conflict — used by Desfecho.AspNetCore to pick an HTTP status code.

ASP.NET Core

Desfecho.AspNetCore turns a Result<TValue> into a minimal API IResult, mapping errors to ProblemDetails (Validation → 400, Unauthorized → 401, Forbidden → 403, NotFound → 404, Conflict → 409).

app.MapPost("/todo-items", async (CreateTodoItemRequest request, ISender sender, CancellationToken ct) =>
{
    var result = await sender.Send(new CreateTodoItemCommand(request.TodoListId, request.Title), ct);
    return result.ToCreated(value => $"/todo-items/{value.Id}");
});

ToOk(), ToCreated(location) and ToNoContent() cover the common cases; errors.ToProblem() is available directly for anything else.

Packages

License

Licensed under the MIT License.