Roslyn Source Generator for .NET that automates Domain-Driven Design patterns and Clean Architecture components.
General
DomainSmith is a set of Roslyn source generators that generate DDD/Clean Architecture boilerplate from simple domain types annotated with attributes:
ValueObject (immutability / value-based equality + factories and updates)
Entity (ID + create/update API)
AggregateRoot (ID + support for entity collections inside the aggregate)
Repository (repository interface for an Aggregate Root)
The generator does not replace your domain logic. Its goal is to generate a consistent API and extensions (for example Create(...), Update(...), entity-collection helpers, etc.) from the fields/properties you already defined.
Packages in src/ are independent and target netstandard2.0 (generators are consumed by application projects). Additionally, DomainSmith.Abstraction provides shared DDD primitives (ValueObject, Entity<TId>, AggregateRoot<TId>) and a lightweight Result pattern.
EntityCollections – the generator analyzes the class and detects entity collections for which it should generate collection-management APIs.
What gets generated:
// <auto-generated/>
using DomainSmith.Abstraction.Common;
using DomainSmith.Abstraction.Core.Primitives;
using DomainSmith.Entity;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using System.Text.Json;
using DomainSmith.Abstraction.Core.Result;
using System.Linq;
using DomainSmith.Abstraction.Common;
using DomainSmith.Abstraction.Core.Result;
namespace DomainSmith.AggregateRoot.Examples.AggregateRoots;
partial class Owner : AggregateRoot<OwnerId>
{
private Owner(OwnerId id, string firstname, string lastname, string email) : base(id)
{
FirstName = firstname;
LastName = lastname;
Email = email;
}
public static Result<Owner> Create(string firstname, string lastname, string email)
{
bool canCreate = true;
Error error = Error.None;
OnCreatingAuto(ref firstname, ref lastname, ref email, ref canCreate, ref error);
OnCreating(ref firstname, ref lastname, ref email, ref canCreate, ref error);
var result = new Owner(new OwnerId(Guid.NewGuid()), firstname, lastname, email);
OnCreated(result, ref canCreate, ref error);
if(!canCreate) return Result.Failure<Owner>(error);
return Result.Success(result);
}
public Result<bool> Update(string firstname, string lastname, string email)
{
bool canUpdate = true;
Error error = Error.None;
OnUpdatingAuto(ref firstname, ref lastname, ref email, ref canUpdate, ref error);
OnUpdating(ref firstname, ref lastname, ref email, ref canUpdate, ref error);
var tmpFirstName = FirstName;
var tmpLastName = LastName;
var tmpEmail = Email;
FirstName = firstname;
LastName = lastname;
Email = email;
OnUpdated(ref canUpdate, ref error);
if(!canUpdate)
{
FirstName = tmpFirstName;
LastName = tmpLastName;
Email = tmpEmail;
return Result.Failure<bool>(error);
}
return Result.Success(true);
}
private static void OnCreatingAuto(ref string firstname, ref string lastname, ref string email, ref bool canCreate, ref Error error)
{
OnCreatingFirstName(ref firstname, ref canCreate, ref error);
OnCreatingLastName(ref lastname, ref canCreate, ref error);
OnCreatingEmail(ref email, ref canCreate, ref error);
}
private void OnUpdatingAuto(ref string firstname, ref string lastname, ref string email, ref bool canUpdate, ref Error error)
{
OnUpdatingFirstName(ref firstname, ref canUpdate, ref error);
OnUpdatingLastName(ref lastname, ref canUpdate, ref error);
OnUpdatingEmail(ref email, ref canUpdate, ref error);
}
static partial void OnCreating(ref string firstname, ref string lastname, ref string email, ref bool canCreate, ref Error error);
static partial void OnCreated(Owner result, ref bool canCreate, ref Error error);
partial void OnUpdating(ref string firstname, ref string lastname, ref string email, ref bool canUpdate, ref Error error);
partial void OnUpdated(ref bool canUpdate, ref Error error);
static partial void OnCreatingFirstName(ref string firstname, ref bool canCreate, ref Error error);
static partial void OnCreatingLastName(ref string lastname, ref bool canCreate, ref Error error);
static partial void OnCreatingEmail(ref string email, ref bool canCreate, ref Error error);
partial void OnUpdatingFirstName(ref string firstname, ref bool canUpdate, ref Error error);
partial void OnUpdatingLastName(ref string lastname, ref bool canUpdate, ref Error error);
partial void OnUpdatingEmail(ref string email, ref bool canUpdate, ref Error error);
public IReadOnlyCollection<Car> NewCars => _newCars;
public Result<Car> AddNewElementToNewCars(string name, string type, decimal price)
{
var result = Car.Create(name, type, price);
if (result.IsFailure)
return result;
var entity = result.Value();
_newCars.Add(entity);
return entity;
}
public Result UpdateElementInNewCars(CarId id, string name, string type, decimal price)
{
var entity = _newCars.FirstOrDefault(a => a.Id == id);
if (entity is null)
return Result.Failure(new Error("Owner.NewCars", "Not found"));
var result = entity.Update(name, type, price);
return result;
}
public Result DeleteElementFromNewCars(CarId id)
{
var entity = _newCars.FirstOrDefault(a => a.Id == id);
if (entity is null)
return Result.Failure(new Error("Owner.NewCars", "Not found"));
_newCars.Remove(entity);
return Result.Success();
}
public IReadOnlyCollection<Car> OldCars => _oldCars;
public Result<Car> AddNewElementToOldCars(string name, string type, decimal price)
{
var result = Car.Create(name, type, price);
if (result.IsFailure)
return result;
var entity = result.Value();
_oldCars.Add(entity);
return entity;
}
public Result UpdateElementInOldCars(CarId id, string name, string type, decimal price)
{
var entity = _oldCars.FirstOrDefault(a => a.Id == id);
if (entity is null)
return Result.Failure(new Error("Owner.OldCars", "Not found"));
var result = entity.Update(name, type, price);
return result;
}
public Result DeleteElementFromOldCars(CarId id)
{
var entity = _oldCars.FirstOrDefault(a => a.Id == id);
if (entity is null)
return Result.Failure(new Error("Owner.OldCars", "Not found"));
_oldCars.Remove(entity);
return Result.Success();
}
}
a consistent API for aggregate creation (Create(...)) and modification (Update(...)),
integration with AggregateRoot<TId> (from DomainSmith.Abstraction),
Result-based variants (default) or non-Result variants (with [NoResultPattern]),
helpers for managing entity collections inside the aggregate.
EntityCollections in AggregateRoot
If the generator detects that the aggregate has an entity collection (for example with a backing field), it generates:
optionally, an IReadOnlyCollection<T> property exposing the collection,
helper methods for collection management:
AddNewElementTo{CollectionName}(...)
UpdateElementIn{CollectionName}(id, ...)
DeleteElementFrom{CollectionName}(id)
Result pattern variants:
with Result pattern:
Add... returns Result<TElement>
Update... / Delete... return Result
when an element is not found, it returns Result.Failure(new Error("{Aggregate}.{Collection}", "Not found"))
without Result pattern:
Add... returns TElement? (null on failure)
Update... / Delete... are void (silent failure, e.g., element not found)
Additionally, the generator detects whether the element entity itself uses the Result pattern (for example TElement.Create(...) may return Result<TElement>). In that case the generated code can:
call TElement.Create(...)
short-circuit and propagate the failure (or return null) if creation/update fails.
Repository (for an Aggregate Root)
The repository generator is based on types annotated with [AggregateRoot].
Input:
using DomainSmith.AggregateRoot;
namespace DomainSmith.Repository.Examples.AggregateRoots;
[AggregateRoot(typeof(Guid))]
public partial class Owner
{
public string FirstName { get; private set; }
public string LastName { get; private set; }
public string Email { get; private set; }
}
an Aggregate Root class annotated with [AggregateRoot(typeof(TId))]
the ID type TId
What gets generated:
// <auto-generated/>
using DomainSmith.AggregateRoot;
using DomainSmith.Abstraction.Core.Primitives;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using System.Text.Json;
using DomainSmith.Abstraction.Core.Maybe;
namespace DomainSmith.Repository.Examples.AggregateRoots;
public interface IOwnerRepository
{
Task<DomainSmith.Abstraction.Core.Maybe.Maybe<Owner>> GetByIdAsync(Guid id, CancellationToken cancellationToken = default);
Task<IReadOnlyCollection<Owner>> GetAllAsync(Guid id, CancellationToken cancellationToken = default);
Task AddAsync(Owner owner, CancellationToken cancellationToken = default);
void Remove(Owner owner);
}
a repository interface named I{AggregateRootName}Repository (the output filename is set explicitly in the generator),
method signatures tailored to the aggregate ID,
Maybe-based GetByIdAsync(...) to represent the possibility of a missing entity.
Practical notes
For source generators, the target type should typically be partial and have stable properties that define the generated API.
If you do not want a member to participate in generation (technical fields, caches, etc.), mark it with [ExcludeFromGeneration].
If you do not use the Result pattern, add [assembly: NoResultPattern] or annotate individual types with [NoResultPattern].
