Ich bin neu im CQRS-Muster, möchte aber verstehen, warum Sie zwei Schnittstellen verwenden sollten:

public interface IQuery{}
public interface ICommand{}

Anstelle von nur einer Schnittstelle (zum Beispiel IExecutable oder was auch immer ...)
Dann haben Sie auch einen Handler (zum Beispiel IExecutionHandler oder was auch immer ...)
Und wenn Sie möchten, können Sie es trotzdem in einen ICommandExecutionHandler und einen IQueryExecutionHandler aufteilen.

Update: ein Versuch

Next Code ist nur ein Beispiel dafür, wie ich es sehe. Es ist möglich, dass ich völlig falsch liege. Teilen Sie also bitte Ihre Bedenken / meine Fehler mit. Ich versuche nur, das zu verstehen.

public interface IExecutable { }

public interface ICommand : IExecutable { }

public interface IReturnCommand<TOutput>: ICommand
{
    TOutput Result { get; set; }
}

public interface IQuery<TOutput>: IExecutable
{
    TOutput Result { get; set; }
}

public interface IExecutionHandler<in T>: IDisposable where T : IExecutable
{
    void Execute(T executable);
}

public class CreateAttachments : IReturnCommand<List<Guid>>
{
    public List<Attachment> Attachments { get; set; }

    public List<Guid> Result { get; set; }    
}

public abstract class BaseExecutionHandler : IDisposable
{
    protected readonly IUnitOfWork UnitOfWork;
    private bool _disposed;

    protected BaseExecutionHandler(IUnitOfWork unitOfWork)
    {
        UnitOfWork = unitOfWork;
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            if (disposing)
            {
                UnitOfWork.Dispose();
            }
        }
        _disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
}

public class AttachmentCommandHandler : BaseExecutionHandler,
    IExecutionHandler<CreateAttachments>
{
    public AttachmentCommandHandler(IUnitOfWork unitOfWork) : base(unitOfWork)
    {
    }

    public void Execute(CreateAttachments command)
    {
        command.Result =  command.Attachments.Select(x => UnitOfWork.Create(x)).ToList();
    }
}

public interface IProcessor : IDisposable
{
    void Process<TExecutable>(TExecutable command) where TExecutable : IExecutable;
}

public class Processor : IProcessor
{
    private readonly Dictionary<IExecutable, IExecutionHandler<IExecutable>> _handlers;
    private readonly IUnitOfWork _unitOfWork;
    private bool _disposed;

    public Processor(IUnitOfWork unitOfWork)
    {
        _handlers = new Dictionary<IExecutable, IExecutionHandler<IExecutable>>();
        _unitOfWork = unitOfWork;
    }

    private IExecutionHandler<IExecutable> GetHandler<TExecutable>(TExecutable executable) where TExecutable: IExecutable
    {
        if (_handlers.ContainsKey(executable))
        {
            return _handlers[executable];
        }
        var handlerType = typeof(IExecutionHandler<>).MakeGenericType(executable.GetType());
        var handler = Activator.CreateInstance(handlerType, _unitOfWork) as IExecutionHandler<IExecutable>;
        _handlers.Add(executable, handler);
        return handler;
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            if (disposing)
            {
                foreach (var handler in _handlers.Values)
                {
                    handler.Dispose();
                }
            }
        }
        _disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    public void Process<TExecutable>(TExecutable executable) where TExecutable : IExecutable
    {
        var handler = GetHandler(executable);
        handler.Execute(executable);
    }
}

public class AttachmentController : ApiController
{
    private readonly IProcessor _processor;

    public AttachmentController(IProcessor processor)
    {
        _processor = processor;
    }

    public List<Guid> Post(List<Attachment> attachments)
    {
        var command = new CreateAttachments { Attachments = attachments };
        _processor.Process(command);
        return command.Result;
    }

    [EnableQuery]
    public IQueryable<Attachment> Get()
    {
        var query = new GetAllAttachments { };
        _processor.Process(query);
        return query.Result;
    }

    protected override void Dispose(bool disposing)
    {
        _processor.Dispose();
        base.Dispose(disposing);
    }
}