泛型和 Com Visible .NET 库 [英] Generics and Com Visible .NET libraries

问题描述

我开发了一个 VB.NET 库(部分也是基于 C# 开发的)，它严重依赖于从抽象泛型基类继承，我正在尝试找出最佳实践.我很遗憾必须使用框架 3.5 来完成.

I've developed a VB.NET library (partially developed on C# as well) that heavily depends on inheriting from an abstract generic base class, and I'm trying to figure out the best practice for this. I Sadly have to do it using framework 3.5.

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

我附加 .tlb 文件作为 VBA 中的参考(使用 Excel)，然后运行以下代码:

I attach the .tlb file as a reference in VBA (using Excel), and I run the following code:

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

我收到错误运行时错误 430:类不支持自动化或不支持预期的接口".

And I get the error "Run-time error 430: Class does not support Automation or does not support expected interface".

另一方面，我将第一行更改为:

On the other hand, I change the first lines to:

Public MustInherit Class MyBaseClass
  Public Whatever As String
End Class

Public Class MyDerivedClass
  Inherits MyBaseClass

VBA 脚本有效.因此，我认为问题出在泛型上(正如其他来源中所记录的那样).但是，删除我的库的通用特性是不可能的.我能想到的最佳"解决方法是编写第三个类，其中包含 MyDerivedClass 作为一个字段，并作为它的非泛型接口工作:

The VBA script works. Hence I assume the issue is with generics (as documented in other sources as well). Dropping the generic feature of my library is not possible, though. The "best" workaround I can think of is to write a third class that includes MyDerivedClass as a field, and works as a non-generic interface to it:

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

这样我就可以像在 VBA 中那样使用它:

This way I can work with it pretty much as I'd like to in VBA:

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

顺便说一句，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 库由几十个类组成.

By the way I think that there might be another (better) way to achieve the same result, and i really hope so since m library is made up of dozens of classes.

非常感谢.

推荐答案

正如我在 MS Office 应用程序的评论编写库 (dll) 中提到的，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:

As i mentioned in comment writing library (dll) for MS Office applications is bit... hard-coded. This dll must exposes methods and properties to be able to use it in COM automation. To be able to achieve that, you need to write interface(s):

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

然后在 DerivedClass 中

then in DerivedClass

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 - 点击 Assembly Information 按钮并在下一个窗口中选择 Make assembly COM visible 复选框(使用 应用设置确定按钮)，

Now, go to Project Properties window 1) choose Application tab - click on Assembly Information button and in the next window select Make assembly COM visible checkbox (apply setting using OK button),

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

2) choose Compile tab - select Register for COM interop checkbox

3) 保存项目并构建 dll

3) Save project and Build dll

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

4) Now, go to VBA Code editor in Office application -> References menu. In Reference window add reference to yourDllName.tlb

现在，您可以在 Office 应用程序中使用您的 dll 了；)

Now, you can use your dll in Office application ;)

我测试过代码:

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；)

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