使用继承对象类型时传递基对象类型

这是实现这一目标的一种方法:

Imports System.Reflection
Module main_
    Sub Main()
        Dim t As New Truck
        Dim c As New Car
        Dim v As Vehicle
        v = t
        SetFlat(v)
        v = c
        SetFlat(v)
    End Sub
    Sub SetFlat(ByVal v As Vehicle)

        Dim vehicletype As Type
        Dim members() As PropertyInfo

        vehicletype = v.GetType
        members = vehicletype.GetProperties

        Console.Write("v is a " & vehicletype.ToString)
        For Each m As PropertyInfo In members
            If m.Name = "IsFlatbed" Then
                m.SetValue(v, True, Nothing)
                Console.WriteLine(" and now it's a flatbed")
                Exit Sub
            End If
        Next
        Console.WriteLine(" so flatbed doesn't apply")
    End Sub
End Module

v is a Vehicles.Truck and now it's a flatbed
v is a Vehicles.Car so flatbed doesn't apply

SetFlat IsFlatbed ,对吧?

那么你应该声明一个接口 Flattable Truck 将实现该接口,并且 刚毛 潜艇会有一个 平板

编辑:

Public Interface IFlattable
    Property IsFlatbed() As Boolean
End Interface

Public Class Truck
    Inherits Vehicle
    Implements IFlattable

    Private _isFlatBed as Boolean
    Public Property IsFlatbed() as Boolean Implements IFlattable.IsFlatbed
        Get
            Return _isFlatbed
        End Get
        Set(ByVal value as Boolean)
            _isFlatbed = value
        End Set
End Class


Public v As Vehicle
Sub WhichVehicle()
    Select Case cmbVehicle.SelectedItem
        Case Truck
            v = New Truck
            SetFlat (DirectCast(v, IFlattable))
        Case Car
            v = New Car
    End Select
End Sub

Sub SetFlat (myVehicle As Flattable)
    myVehicle.IsFlatbed = True
End Sub

我找到了两种可能对你有帮助的方法。

它可能看起来像(我不是VB.Net程序员,所以可能有一些错误):

Sub SetFlat(of T) (myVehicle As T)
    T.IsFlatbed = True
End Sub
// later you can just call
SetFlat(Of Truct)(myVehicle)  

当然这意味着您需要在调用之前知道myVehicle对象的确切类型 SetFlat函数。同时,SetFlat只能与具有isflated属性的类一起调用。 有关VB.Net中泛型的更多详细信息:
http://www.15seconds.com/issue/040526.htm
http://msdn.microsoft.com/en-us/library/w256ka79%28VS.80%29.aspx
Generic Functions in VB.NET

第二个(脏)解决方案是使用.Net反射来检测myVehicle对象是否包含IsFlatbed属性。您可以在以下方面找到更多详细信息:
http://msdn.microsoft.com/en-us/magazine/cc163750.aspx
http://visualbasic.about.com/od/usingvbnet/a/proginfo.htm
http://www.eggheadcafe.com/community/aspnet/14/14989/reflection.aspx

我决定启动Visual Studio并进行一些测试,因为我对其他答案的评论可能没有多大意义。假设您有以下类:

Public Class Vehicle
   Public Property Model As String
   Public Property Make As String
End Class

Public Class Truck : Inherits Vehicle
   Public Property IsFlatbed As Boolean
End Class

Public Class Car : Inherits Vehicle
   Public Property LeatherSeats As Boolean
End Class

您还可以在另一个类中使用以下方法:

Private Sub WhichVehicle()
    Select Case cmbVehicle.SelectedItem
        Case Truck
            v = New Truck
        Case Car
            v = New Car
    End Select

    SetFlat(v)
End Sub

Private Sub SetFlat(ByVal myVehicle As Vehicle)
   If TypeOf myVehicle Is Car Then
      Debug.WriteLine("This is a car")

      Dim c As Car = DirectCast(myVehicle, Car)
      c.LeatherSeats = False
   ElseIf TypeOf myVehicle is Truck Then
      Debug.WriteLine("This is a truck")

      Dim t As Truck = DirectCast(myVehicle, Truck)
      t.IsFlatbed = True
   End If
End Sub

所以,这可以让你随心所欲地绕过一个车辆对象,因为直到运行时,你才知道你要处理的具体车辆类型(汽车或卡车)。SetFlat方法可以在运行时确定它通过了哪个特定的车辆子类,并相应地采取行动。您只需确保在确定泛型车辆对象(v)是哪种类型的子类(对于Car是c,对于Truck是t)之后,将泛型车辆对象(v)转换为更具体的子类的新对象,否则代码将不会编译,因为您将尝试调用泛型车辆类型上不存在的方法,但仅限于特定车型。

我看到这种方法最大的缺点是,如果有很多代码,它可能会变得乏味。这是因为要调用的每个方法都必须检查传递给它的特定vehicle对象的类型,并根据该特定类型运行一组不同的例程。

我认为你应该提供更多的细节关于你想做什么。。。 typeof

Dim v as Vehicle
'...
If typeof v is Truck then SetFlat(DirectCast(v, Truck))

编辑 :SetFlat应该以Truck作为参数,只有这样才有意义。