VB.NET: "AddHandler"通过将 Handler 函数指定为变量

Question

我正在为 Autodesk Inventor(一种 3D CAD 程序)编写插件。该插件向 Inventor 添加了一堆内部命令，并为每个命令创建了一个工具栏按钮。我需要将每个命令的执行事件连接到我的加载项中的处理函数。

我创建了一个“MyCommand”类，其中包含定义命令所需的所有信息。我还创建了一个 List(Of MyCommand)，其中包含每个命令的定义。最后，我可以遍历每个命令并创建内部 Inventor 命令定义，以及将按钮添加到工具栏。但是，我不知道如何在循环内 将命令与其处理程序函数相关联。

下面的示例代码说明了我所追求的:

Sub CreateCommands()
    Dim oCommands As New List(Of MyCommand)

    oCommands.Add(New MyCommand("DrawLogoCmd", "Draw Logo", "DrawLogoSub"))
    oCommands.Add(New MyCommand("PublishDrawingCmd", "Publish Drawing", "PublishDrawingSub"))
    ' [Dozens more commands]

    For Each oCommand As MyCommand In oCommands
        ' Code for adding internal command definition and button to Inventor. This is working fine.
        Dim oCommandDef As Inventor.CommandDefinition = InventorApp.CommandDefinitions.Add(oCommand.InternalDefinitionName, oCommand.DisplayName)
        InventorApp.ToolbarButtons.Add(oCommandDef)

        ' Associate command definition with handler function
        ' ===== THIS IS THE LINE I NEED TO FIGURE OUT =====
        AddHandler oCommandDef.OnExecute, AddressOf oCommand.HandlerSubName
    Next
End Sub

Sub DrawLogoSub()
    ' [My add-in's code to draw logo in Inventor]
End Sub

Sub PublishDrawingSub()
    ' [My add-in's code to publish drawing in Inventor]
End Sub

Class MyCommand
    Public InternalDefinitionName As String
    Public DisplayName As String
    Public HandlerSubName As String

    Sub New(InternalDefinitionName As String, DisplayName As String, HandlerSubName As String)
        With Me
            .InternalDefinitionName = InternalDefinitionName
            .DisplayName = DisplayName
            .HandlerSubName = HandlerSubName
        End With
    End Sub
End Class

那么，这可能吗？有什么方法可以使用它的名称作为字符串来获取“AddressOf”我的函数吗？或者，是否有某种方法可以在我的 MyCommand 类中存储对函数本身的引用，并将其传递给 AddressOf 运算符？

或者，除了“AddHandler/AddressOf”之外，还有其他可行的方法吗？

如有任何建议，我们将不胜感激。

Answer 1

是的，您可以使用反射按名称找到该方法，但我不推荐这样做。 AddHandler 命令通常被赋予 AddressOf 方法，但它也可以采用委托(delegate)，只要它符合事件的签名。因此，除非您需要通过字符串来完成，否则我建议您改为这样做。假设事件匹配普通的 EventHandler 委托(delegate):

Sub CreateCommands()
    Dim oCommands As New List(Of MyCommand)

    oCommands.Add(New MyCommand("DrawLogoCmd", "Draw Logo", AddressOf DrawLogo))
    oCommands.Add(New MyCommand("PublishDrawingCmd", "Publish Drawing", AddressOf PublishDrawing))
    ' [Dozens more commands]

    For Each oCommand As MyCommand In oCommands
        ' Code for adding internal command definition and button to Inventor. This is working fine.
        Dim oCommandDef As Inventor.CommandDefinition = InventorApp.CommandDefinitions.Add(oCommand.InternalDefinitionName, oCommand.DisplayName)
        InventorApp.ToolbarButtons.Add(oCommandDef)

        ' Associate command definition with handler function
        AddHandler oCommandDef.OnExecute, oCommand.Handler
    Next
End Sub

Sub DrawLogo(sender As Object, e As EventArgs)
    ' [My add-in's code to draw logo in Inventor]
End Sub

Sub PublishDrawing(sender As Object, e As EventArgs)
    ' [My add-in's code to publish drawing in Inventor]
End Sub

Class MyCommand
    Public InternalDefinitionName As String
    Public DisplayName As String
    Public Handler As EventHandler

    Sub New(InternalDefinitionName As String, DisplayName As String, Handler As EventHandler)
        With Me
            .InternalDefinitionName = InternalDefinitionName
            .DisplayName = DisplayName
            .Handler = Handler
        End With
    End Sub
End Class

如果你真的需要通过字符串来完成，你可以像这样使用反射(注意我使用了 NameOf 而不是将方法名称硬编码为字符串文字，只是为了更安全) :

Sub CreateCommands()
    Dim oCommands As New List(Of MyCommand)

    oCommands.Add(New MyCommand("DrawLogoCmd", "Draw Logo", NameOf(DrawLogo)))
    oCommands.Add(New MyCommand("PublishDrawingCmd", "Publish Drawing", NameOf(PublishDrawing)))
    ' [Dozens more commands]

    For Each oCommand As MyCommand In oCommands
        ' Code for adding internal command definition and button to Inventor. This is working fine.
        Dim oCommandDef As Inventor.CommandDefinition = InventorApp.CommandDefinitions.Add(oCommand.InternalDefinitionName, oCommand.DisplayName)
        InventorApp.ToolbarButtons.Add(oCommandDef)

        ' Associate command definition with handler function
        AddHandler oCommandDef.OnExecute, Sub(sender As Object, e As EventArgs) CallMethod(oCommand.Handler)
    Next
End Sub

Private Sub CallMethod(name As String)
    Me.GetType().GetMethod(name).Invoke(Me, Nothing)
End Sub

Sub DrawLogo()
    ' [My add-in's code to draw logo in Inventor]
End Sub

Sub PublishDrawing()
    ' [My add-in's code to publish drawing in Inventor]
End Sub