vb.net - 依赖注入(inject) - 我不明白!

Question

好的，所以我在玩 Ninject，一个“服务层”和一个“存储库层”。

我构建了一个简单的控制台应用程序来玩，这就是我想出的:

Imports Ninject

Module Module1

    Sub Main()
        Dim Kernel As IKernel = New StandardKernel(New CustomerModule)
        Dim Service = Kernel.Get(Of CustomerService)()
        Console.WriteLine(Service.GetCustomerByID(1).Name)
        Console.Read()

    End Sub

End Module

#Region "Services"

Public Class CustomerService
    Private _Repository As ICustomerRepository

    <Inject()> _
    Public Sub New(ByVal Repository As ICustomerRepository)
        _Repository = Repository

    End Sub

    Public Function GetCustomerByID(ByVal ID As Integer) As Customer
        Return _Repository.GetByID(ID)
    End Function

End Class

#End Region

#Region "Repositories"

Public Interface IRepository(Of T)
    Function Query(ByVal Predicate As Expressions.Expression(Of Func(Of T, Boolean))) As IQueryable(Of T)
    Function GetByID(ByVal ID As Integer) As T

End Interface

Public Interface ICustomerRepository
    Inherits IRepository(Of Customer)

End Interface

Public Class CustomerRepository
    Implements ICustomerRepository

    Public Function GetByID(ByVal ID As Integer) As Customer Implements IRepository(Of Customer).GetByID
        Return New Customer With {.ID = ID, .Name = "Sam Striano"}
    End Function

    Public Function Query(ByVal Predicate As System.Linq.Expressions.Expression(Of System.Func(Of Customer, Boolean))) As System.Linq.IQueryable(Of Customer) Implements IRepository(Of Customer).Query
        Return Nothing
    End Function

End Class

#End Region

#Region "Domain Objects"

Public Class Customer
    Public Property ID As Integer
    Public Property Name As String
End Class

#End Region

#Region "Ninject Modules"

Public Class CustomerModule
    Inherits Modules.NinjectModule

    Public Overrides Sub Load()
        Bind(Of ICustomerRepository).To(Of CustomerRepository)()

    End Sub

End Class

#End Region

我的问题，或者我猜我缺乏理解，在于模块的 Main() 方法:

Sub Main()
    Dim Kernel As IKernel = New StandardKernel(New CustomerModule)
    Dim Service = Kernel.Get(Of CustomerService)()
    Console.WriteLine(Service.GetCustomerByID(710615).Name)
    Console.Read()

End Sub

为什么不这样做:

Sub Main()
    Dim Service = New CustomerService(New CustomerRepository)
    Console.WriteLine(Service.GetCustomerByID(710615).Name)
    Console.Read()

End Sub

Answer 1

基本上，您是在问为什么要使用 DI 容器 而不是 Pure DI .

DI 真的只是一个 一套原则和模式启用 松耦合 .您可以使用这些模式来编写应用程序 不考虑任何特定容器 .

但是，随着应用程序复杂性的增加，尤其是当您需要管理 时不同的生活方式在您的组件中，DI 容器是一个出色的工具，可以解决您必须手动解决的许多问题。