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POWhat is the difference between Domain Handlers and Application Services in Project Silk?
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copied!<p>This is specifically in reference usage of DDD in <a href="http://msdn.microsoft.com/en-us/library/hh404097.aspx" rel="nofollow">Project Silk</a> .</p> <p>The project uses DDD and has the concept of <strong>Handlers</strong> and <strong>Services</strong> implemented. What exactly is the difference and use case for these 2 types?</p> <p>For instance, there is a service <code>UserServices</code> for creation of User. But the creation fo Vehicle is done in a Handler.</p> <p>Would like to know the reasoning behind this decision.</p> <p><strong>Domain\UserServices</strong></p> <pre><code>public class UserServices : IUserServices { private readonly IUserRepository userRepository; public UserServices(IUserRepository userRepository) { if (userRepository == null) throw new ArgumentNullException("userRepository"); this.userRepository = userRepository; } public User CreateUser(User newUser) { if (newUser == null) throw new ArgumentNullException("newUser"); try { Model.User userToAdd = ToDataModelUser(newUser); this.userRepository.Create(userToAdd); return ToServiceUser(userToAdd); } catch (InvalidOperationException ex) { throw new BusinessServicesException (Resources.UnableToCreateUserExceptionMessage, ex); } } } </code></pre> <p><strong>Domain\Handlers\CreateVehicle.cs</strong></p> <pre><code>public class CreateVehicle { private readonly IVehicleRepository _vehicleRepository; private readonly IVehiclePhotoRepository _photoRepository; public CreateVehicle(IVehicleRepository vehicleRepository, IVehiclePhotoRepository photoRepository) { _vehicleRepository = vehicleRepository; _photoRepository = photoRepository; } public virtual void Execute(int userId, ICreateVehicleCommand vehicleForm, HttpPostedFileBase photoFile) { if (vehicleForm == null) throw new ArgumentNullException("vehicleForm"); try { var vehicle = vehicleForm.ConvertToEntity(userId); _vehicleRepository.Create(userId, vehicle); if (photoFile == null) return; // the double reference between vehicle and photo //is a potential source of pain var photo = photoFile.ConvertToEntity(); _photoRepository.Create(vehicle.VehicleId, photo); vehicle.PhotoId = photo.VehiclePhotoId; _vehicleRepository.Update(vehicle); } catch (InvalidOperationException ex) { throw new BusinessServicesException (Resources.UnableToCreateVehicleExceptionMessage, ex); } } } </code></pre>

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