Vb.net 如何将lambda函数作为条件参数的默认值传递到常规函数中？

以下是：

Delegate Function OperationDelegate(ByVal x As Double) As Double
Public Function test(Optional ByRef operation As OperationDelegate = AddressOf DefaultOperation) As Double
    Return operation.Invoke(3)
End Function

给我一个错误：常量表达式是必需的。Addressof DefaultOperation导致使用Visual Studio 2013时出错

我尝试过用以下两种方法定义DefaultOperation

Public Function DefaultOperation(ByVal x As Double) As Double
    Return x
End Function

Dim DefaultOperation As OperationDelegate = Function(x As Double) As Double
                                                Return x
                                            End Function

无论哪种情况，它都没有起作用。 这是我一直在使用的资源：

无论如何，谢谢你的时间

我发现了一个类似的问题：

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正如您在原始帖子上的评论所建议的，lambda不能用作可选参数

Delegate Function OperationDelegate(ByVal x As Double) As Double

Public Function test() As Double
   Return test(AddressOf OperationDelegate)
End Function

Public Function test(operation As OperationDelegate) As Double
   Return operation.Invoke(3)
End Function

另一种方法是使用不带参数的版本和带有委托参数的版本重载函数（在您的示例中为test）

Delegate Function OperationDelegate(ByVal x As Double) As Double

Public Function test() As Double
   Return test(AddressOf OperationDelegate)
End Function

Public Function test(operation As OperationDelegate) As Double
   Return operation.Invoke(3)
End Function

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正如您从链接到的类似问题中所看到的。可选参数的默认值必须是常量（其值必须在编译时已知）。不可能是兰姆达。