C# 实体框架和存储库模式

Question

使用工作单元和存储库模式，我有以下几点：

public interface IDatabaseFactory<C> : IDisposable
{
    C Get();
    void Set(string connectionString);
}

public interface IUnitOfWork<C>
{
    ICustomerRepository Customers { get; }
    //etc...

    void Commit();
    void ChangeDatabase(string connectionString);
    string GetConnectionString(Database database);
}

public interface ICustomerRepository : IRepository<Customer> { }

以及实现：

public class CustomerRepository : Repository<MyDbContext, Customer>, ICustomerRepository
{
    public CustomerRepository (IDatabaseFactory<MyDbContext> databaseFactory) 
        : base(databaseFactory) { }
}

public class UnitOfWork<C> : IUnitOfWork<C> where C : DbContext, IMyDbContext
{
    private readonly IDatabaseFactory<C> databaseFactory;

    private C dataContext;

    public UnitOfWork(IDatabaseFactory<C> databaseFactory)
    {
        this.databaseFactory = databaseFactory;
    }

    private ICustomerRepository customerRepository;
    public ICustomerRepository Customers
    {
        get { return customerRepository?? (customerRepository = new CustomerRepository((IDatabaseFactory<MyDbContext>)databaseFactory)); }
    }

    private void ClearRespositories()
    {
        customerRepository = null;
    }

    protected C DataContext
    {
        get { return dataContext ?? (dataContext = databaseFactory.Get()); }
    }

    public string GetConnectionString(Model.Database database)
    {
    }

    public void ChangeDatabase(string connectionString)
    {
    }

    public void Commit()
    {
    }
}

我的模型有不少于 250 个主要实体，使用上述模式，它们需要相同数量的存储库，并且每一个都是工作单元类中的一个属性。

我的典型服务层类是：

public class CustomerService : BaseService, ICustomerService
{
    private ICustomerRepository customerRepository;

    public CustomerService(IUnitOfWork<MyDbContext> unitOfWork) : base(unitOfWork) { }

    public override void ChangeDatabase(string connectionString)
    {
        base.ChangeDatabase(connectionString);
        customerRepository = unitOfWork.Customers;
    }
}

我的应用程序有一个数据库上下文，并且此上下文用于不同的数据库（使用相同的上下文）。当用户登录系统时，他可以选择一个数据库，这将相应地设置 uow 类的数据上下文。

我已将存储库添加到 UoW 类，以便所有存储库都具有相同的 uow。

这是正确的方法还是有更好的方法？

Answer 1

您可以使用通用存储库模式。这可以通过非常具体的域查询来扩展。然后，您的 DI 容器可以创建您需要的特定存储库，您可以针对所有数据类使用它。

如果对代码有任何疑问，请随时提出。

我会给你我的VB.net代码，希望它有用：

这是您将要使用的界面。保存和检索您的类（它们必须从 IEntity 继承）

Public Interface IRepository
    Function GetEntity(Of T As {EntityObject, IEntity})(id As Integer) As T

    Function GetAll(Of T As {EntityObject, IEntity})() As IEnumerable(Of T)

    Sub Add(Of T As {EntityObject, IEntity})(entity As T)
    Sub Remove(Of T As EntityObject)(entity As T)
    Sub Attach(Of T As EntityObject)(entity As T)
    Sub Update(Of T As {EntityObject, IEntity})(entity As T)

    Function ExecuteQuery(Of T As {EntityObject, IEntity})(query As IQuery(Of T)) As IQueryResult(Of T)
    Function ExecuteQuery(Of T As {EntityObject, IEntity}, TResult)(query As IQuery(Of T, TResult)) As IQueryResult(Of TResult)
End Interface

您必须在数据对象中实现的接口 您也可以使用其他 int 进行 PK：

Public Interface IEntity
    Property Id As Int32
End Interface

IQuery 对象，对您的数据进行特定查询：

Public Interface IQuery(Of T As {EntityObject, IEntity})
    Function Execute(ByVal objectSet As ObjectSet(Of T)) As IQueryResult(Of T)
End Interface

Public Interface IQuery(Of T As {EntityObject, IEntity}, TResult)
    Function Execute(ByVal objectSet As ObjectSet(Of T)) As IQueryResult(Of TResult)
End Interface

您将使用的 QueryResult，它是可扩展的

Public Interface IQueryResult(Of T)
    Function UniqueResult() As T
    Function List() As IEnumerable(Of T)
End Interface

Public Class LinqResult(Of T)
    Implements IQueryResult(Of T)
    Private ReadOnly _query As IQueryable(Of T)

    Public Sub New(query As IQueryable(Of T))
        _query = query
    End Sub

    Protected Overridable Function ExpandQuery(query As IQueryable(Of T)) As IQueryable(Of T)
        Return query
    End Function

    Public Function UniqueResult() As T Implements IQueryResult(Of T).UniqueResult
        Dim result = ExpandQuery(_query).SingleOrDefault()
        If result Is Nothing Then
            Throw New EntityNotFoundException(Of T)()
        End If
        Return result
    End Function
    Public Function List() As IEnumerable(Of T) Implements IQueryResult(Of T).List
        Return ExpandQuery(_query).ToList()
    End Function
End Class

你的 ObjectcontextRepository，你的 IRepository 的实际实现

Public Class EntityObjectContextRepository
    Implements IRepository

    Private ReadOnly Property _context As ObjectContext
        Get
            Return UnitOfWork.Current
        End Get
    End Property


    Public Sub Add(Of T As {EntityObject, IEntity})(entity As T) Implements IRepository.Add
        _context.CreateObjectSet(Of T)().AddObject(entity)
    End Sub

    Public Sub Attach(Of T As EntityObject)(entity As T) Implements IRepository.Attach
        _context.Attach(entity)
        '_context.CreateObjectSet(Of T)().Attach(entity)
    End Sub

    Public Sub Update(Of T As {EntityObject, IEntity})(ByVal entity As T) Implements IRepository.Update
        _context.CreateObjectSet(Of T)().Attach(entity)
        _context.ObjectStateManager.ChangeObjectState(entity, EntityState.Modified)
    End Sub

    Public Function ExecuteQuery(Of T As {EntityObject, IEntity})(query As IQuery(Of T)) As IQueryResult(Of T) Implements IRepository.ExecuteQuery
        Return query.Execute(_context.CreateObjectSet(Of T))
    End Function

    Public Function ExecuteQuery(Of T As {EntityObject, IEntity}, TResult)(ByVal query As IQuery(Of T, TResult)) As IQueryResult(Of TResult) Implements IRepository.ExecuteQuery
        Return query.Execute(_context.CreateObjectSet(Of T))
    End Function

    Public Function GetAll(Of T As {EntityObject, IEntity})() As IEnumerable(Of T) Implements IRepository.GetAll
        Return _context.CreateObjectSet(Of T).ToList().Where(Function(c) c.EntityState <> EntityState.Deleted)
    End Function

    Public Function GetEntity(Of T As {EntityObject, IEntity})(id As Integer) As T Implements IRepository.GetEntity
        Dim entity = _context.CreateObjectSet(Of T)().SingleOrDefault(Function(x) x.Id = id)
        Return ReturnEntityWhenItExists(entity)
    End Function

    Public Sub Remove(Of T As EntityObject)(entity As T) Implements IRepository.Remove
        _context.DeleteObject(entity)
    End Sub

    Private Function ReturnEntityWhenItExists(Of T As {EntityObject, IEntity})(ByVal entity As T) As T
        If entity IsNot Nothing AndAlso entity.EntityState <> EntityState.Deleted Then
            Return entity
        End If
        Throw New EntityNotFoundException(Of T)()
    End Function
End Class

包装这一切的工作单元：

Public Class UnitOfWork
    Implements IDisposable

    Private Shared _dataContext As ObjectContext

    Public Shared ReadOnly Property Current As ObjectContext
        Get
            If _dataContext Is Nothing Then
                Throw New UnitOfWorkException(ResourceRetriever.GetResource(Of String)("ExceptionUnitOfWorkNotInitializedMessage"))
            End If
            Return _dataContext
        End Get
    End Property

    Public Sub New()
        Me.New(New YourDataModelContainer())
    End Sub

    Public Sub New(ByVal objectContext As ObjectContext)
        If _dataContext IsNot Nothing Then
            Throw New UnitOfWorkException(ResourceRetriever.GetResource(Of String)("ExceptionUnitOfWorkAlreadyInitializedMessage"))
        End If
        _dataContext = objectContext
    End Sub

    Public Sub Complete()
        If _dataContext Is Nothing Then
            Throw New UnitOfWorkException(ResourceRetriever.GetResource(Of String)("ExceptionUnitOfWorkNotInitializedMessage"))
        End If
        _dataContext.SaveChanges()
    End Sub

    Public Sub Dispose() Implements IDisposable.Dispose
        If _dataContext IsNot Nothing Then
            _dataContext.Dispose()
            _dataContext = Nothing
        End If
    End Sub
End Class

查询示例：

Public Class GetAllBuildingsQuery
Implements IQuery(Of DataAccess.Building, BuildingDto)

Public Function Execute(ByVal objectSet As ObjectSet(Of Building)) As IQueryResult(Of BuildingDto) Implements IQuery(Of Building, BuildingDto).Execute
    Dim query = objectSet.Select(Function(g) New BuildingDto() With {.Description = g.Name, .Id = g.Id})
    Return New LinqResult(Of BuildingDto)(query)
End Function
End Class

在服务调用中是如何实现的：

Public Class EmployeeService
    Implements IEmployeeService


    Private ReadOnly _repository As IRepository
    Public Sub New(ByVal repository As IRepository)
        _repository = repository
    End Sub

    Public Function GetAllEmployees() As IEnumerable(Of EmployeeOverviewDto) Implements IEmployeeService.GetAllEmployees
        Dim employees = _repository.ExecuteQuery(EmployeeQueries.GetAllEmployeesForOverview()).List()
        Return employees
    End Function
End Class