Generics和Com Visible .NET库

Question

我开发了一个VB.NET库(部分是在C#上开发的),它很大程度上依赖于从一个抽象的泛型基类继承而来,我正试图找出最佳实践.我不得不使用框架3.5来做到这一点.

Public MustInherit Class MyBaseClass(Of T)
  Public Whatever As T
End Class

Public Class MyDerivedClass
  Inherits MyBaseClass(Of String)

  Private _myProperty As String

  Public Property MyProperty As String
    Get
      Return _myProperty
    End Get
    Set(value As String)
      _myProperty = value
    End Set
  End Property
End Class

我将.tlb文件作为VBA中的引用(使用Excel)附加,并运行以下代码:

Dim m As New VBtoVBA.MyDerivedClass
m.MyProperty = "foo"

我得到错误"运行时错误430:类不支持自动化或不支持预期的接口".

另一方面,我将第一行更改为:

Public MustInherit Class MyBaseClass
  Public Whatever As String
End Class

Public Class MyDerivedClass
  Inherits MyBaseClass

VBA脚本有效.因此,我认为问题在于泛型(也在其他来源中有记录).但是,删除我的库的通用功能是不可能的.我能想到的"最佳"解决方法是编写包含MyDerivedClass作为字段的第三个类,并将其作为非泛型接口:

Public Class MyDerivedClassString

  Private _innerObj As New MyDerivedClass

  Public Property MyProperty As String
    Get
      Return _innerObj.MyProperty
    End Get
    Set(value As String)
      _innerObj.MyProperty = value
    End Set
  End Property

  Public Property Whatever As String
    Get
      Return _innerObj.Whatever
    End Get
    Set(value As String)
      _innerObj.Whatever = value
    End Set
  End Property

End Class

这样我可以在VBA中使用它,就像我想要的那样:

m.Whatever = "wha"
MsgBox (m.Whatever)

顺便说一下,我认为可能有另一种(更好的)方法来实现相同的结果,我真的希望如此,因为m库是由几十个类组成的.

非常感谢.

Answer 1

正如我在评论中提到的,为MS Office应用程序编写库(dll)有点......硬编码.此dll必须公开方法和属性才能在COM自动化中使用它.为了能够实现这一点,您需要编写接口:

Namespace VBtoVBA
    Public Interface IMyDerivedClass
        Property MyProperty As String
    End Interface
End Namespace

然后在DerivedClass中

Public Class MyDerivedClass
    Inherits MyBaseClass(Of String)
    Implements IMyDerivedClass

    Private _myProperty As String

    Public Property MyProperty As String Implements IMyDerivedClass.MyProperty

现在,转到Project Properties窗口1)选择Application选项卡 - 单击Assembly Information按钮,然后在下一个窗口中选择Make assembly COM visible复选框(使用OK按钮应用设置),

2)选择Compile选项卡 - 选择Register for COM interop复选框

3)保存项目和构建DLL

4)现在,转到Office应用程序 - > References菜单中的VBA代码编辑器.在Reference window添加参考yourDllName.tlb

现在,您可以在Office应用程序中使用您的DLL;)

我测试了代码:

Option Explicit

Sub DoSomething()
Dim m As VBtoVBA.MyDerivedClass

Set m = New VBtoVBA.MyDerivedClass

m.MyProperty = "Something"

MsgBox m.MyProperty


End Sub

它也有效;)