存储库中或单独的业务类中的业务逻辑？

Question

I'm developing an application where I'm using repositories (repository pattern) that handle all the CRUD operations (I'm using entity framework) and Unit of work for handling the context. I have a generic repository like this:

Public Interface IRepository(Of TEntity As Class)

 Function GetAll() As IEnumerable(Of TEntity)
 Function GetByID(id As Object) As TEntity

End Interface


Public Class Repository(Of TEntity As Class)
  Implements IRepository(Of TEntity)

  Friend _dbContext As Entities = Nothing
  Friend _dbSet As IDbSet(Of TEntity)

  Public Sub New(ByVal context As Entities)
    If context Is Nothing Then
        Throw New ArgumentNullException("context wasn't supplied")
    End If
    Me._dbContext = context
    Me._dbSet = context.Set(Of TEntity)()
  End Sub

  Public Function GetAll() As IEnumerable(Of TEntity) Implements IRepository(Of TEntity).GetAll
    Return _dbSet.ToList().AsQueryable()
 End Function



 Public Overridable Function GetByID(id As Object) As TEntity Implements IRepository(Of     
    TEntity).GetByID
    Return _dbSet.Find(id)
 End Function


End Class


Public Interface IUnitOfWork

  ReadOnly Property PersonRepository() As IRepository(Of Person)
  ReadOnly Property OrgRepository() As IRepository(Of Organization)

  Sub Save()

End Interface


Public Class UnitOfWork
Implements IUnitOfWork
Implements IDisposable

Private _context As Entities
Private _personRepository As IRepository(Of Person)
Private _orgRepository As IRepository(Of Organization)
Private disposed As Boolean = False

Public Sub New()
    Me._context = New Entities
End Sub

Public ReadOnly Property PersonRepository() As IRepository(Of Person) Implements  IUnitOfWork.PersonRepository
    Get
        If Me._personRepository Is Nothing Then
            Me._personRepository = New Repository(Of Person)(_context)
        End If
        Return _personRepository
    End Get
End Property

.
.
.
.

Public Sub Save() Implements IUnitOfWork.Save
    _context.SaveChanges()
End Sub

Public Sub Dispose() Implements IDisposable.Dispose
    Dispose(True)
    GC.SuppressFinalize(Me)
End Sub

Protected Overridable Sub Dispose(disposing As Boolean)
    If Not Me.disposed Then
        If disposing Then
            _context.Dispose()
        End If
    End If
    Me.disposed = True
End Sub

End Class

My problem is the business logic, where should I put it? I need to count up all my persons returned and I have to calculate the total weight of all these persons. Should this be done in the person repository or do I need a separate person class for this? This is not a MVC application, my classes should be used by another application (I have no front end classes).

I have looked at this example

Under the headline “Changing the Course Controller to use the UnitOfWork Class and Repositories” he does this

public ViewResult Details(int id) { 
  Course course = unitOfWork.CourseRepository.GetByID(id); 
  return View(course); 
 } 

How is it possible to say

Course course = unitOfWork.CourseRepository.GetByID(id);

The course object is of type Course but the object returned from unitOfWork.CourseRepository.GetByID(id) is of type course entity (from entity framework).

My last question….can I have any properties in the repository classes. If I should have my function for counting all the people and my total weight function in the repository class I need to also have my properties for name, address and so on for storing information.

I hope sombody can help me :)

Thanks in advance!

Liss

EDIT:

Thanks for your answer! So what you are saying is that if I don't have any heavy logic (that is the case for me) I use an extra Person class where I have my properties an also functions for weight and total number of person, but also functions that "mirrors" the functions (GetAll, GetByID) in the generic repository class. And I use the Person class from other classes not the repository class? I still don't understand the example Course course = unitOfWork.CourseRepository.GetByID(id), her the repository and unit of work is used the same way as I did, I think. But when I try this, the unitOfWork.CourseRepository.GetByID(id) returns an object of entity type but the course is an "ordinary" object type (a ordinary class with only properties). How can I say: object of type A = object of type B?

EDIT 2:

Thanks a lot for taking the time to answer me!! So what you say is that it is sometimes better to not auto generate entities but write POCO class instead? But if I want to use my auto generated entities, and I have an entity named PersonEntity I can use this like this in my controller class like this:

 Dim personEntity As PersonEntity

 personEntity = unitOfWork.PersonEntityRepository.GetByID(id)

But if I do it like this I have a reference to an entity in my controller class, but do I want that? Isn't it best to separate the entities from the controller if I later need to change from Entity Framework? But what I still do not understand is, should I create a new Person class with the same properties as the autogen PersonEntity class and use this in my controller like this

Dim person As Person

person = unitOfWork.PersonEntityRepository.GetByID(id)

But then the unitOfWork.PersonEntityRepository.GetByID(id) will return a object of type PersonEntity… so this is not working. And where should I put my total weight and total persons functions?

If I understand what you are saying, an entity object can be used as a transfer object but it's better to use a POCO/DTO object. But if I use a Person POCO can I still have the PersonEntity object? And how do I populate the POCO object when I return the PersonEntity object?

Answer 1

Regarding "where should I put business logic": There are two approaches:

1. Complex business logic usually goes into a service layer. A service may depend on one or more repositories to perform CRUD operations on your models. Thus a single service operation representing a business operation may depend on multiple simple operations. Then you could reuse this service layer in your controllers and other applications. Use basic POCO/DTOs for data transfer between layers.

2. Use domain entities which contain their own operation logic.

A similar discussion can be found here so please have a look on: Repository pattern and/or/vs business logic layer

And about the example you mentioned which is using

"Course course = unitOfWork.CourseRepository.GetByID(id);"

It is very possible as we can compose the Repository and UoW Patterns in different ways. Please have a look on this question https://softwareengineering.stackexchange.com/questions/151374/relationship-between-repository-and-unit-of-work

and an answer by Wouter de Kort here Entity Framework + Repository + Unit of Work

Yes, you can have properties instead of get methods. I prefer get methods as it gives better uniformity to use a repository.

Hope it would be helpful. Please let me know in case of further questions. Thanks.

Additional Answers after your edit:

You are Welcome. I have downloaded that code for the example and looked again to understand your query but I can see that: both side of the line :"Course course = unitOfWork.CourseRepository.GetByID(id);" refers to same class :ContosoUniversity.Models.Course.

 public ActionResult Edit(int id)
    {
        Course course = unitOfWork.CourseRepository.GetByID(id);
        PopulateDepartmentsDropDownList(course.DepartmentID);
        return View(course);
    }

The code inside following "Details" method of CourseController does not have the same code as shown in the webpage: public ActionResult Details(int id)

Further you can have Person class as a Model class having business logic related to Person inside class. And PersonRepository would have methods like (GetAll, GetByID). If you have many repositories you can create a GenericRepository too as given below:

class GenericRepository<TEntity> where TEntity : class

I hope its fine by now. Further questions are most welcome.