Optional and named parameters in an Attribute..?

[NickThissen]

Hi,

I have a custom Attribute class where the constructor takes one fixed parameter and two optional parameters. It is my understanding that one can supply one or more optional parameters by using 'named parameters' such as this:

Private Sub CallMethod()
   Me.OptionalMethod(-1, z:=1)
End Sub

Private Sub OptionalMethod(ByVal x As Integer, Optional ByVal y As Integer = 0, Optional ByVal z As Integer = 10)
   '...
End Sub

This way I skip the 'y' parameter and simply let it use the default value of 0. This works fine for any class, except apparently for attributes...

This is my attribute class:

<AttributeUsage(AttributeTargets.Property, AllowMultiple:=False)> _
    Public Class GridOptionsAttribute
        Inherits System.Attribute
 
        Public Sub New(ByVal visible As Boolean, Optional ByVal text As String = Nothing, Optional ByVal index As Integer = -1)
            _DisplayName = text
            _Visible = visible
            _DisplayIndex = index
        End Sub
 
        Private _DisplayName As String
        Public ReadOnly Property DisplayName() As String
            Get
                Return _DisplayName
            End Get
        End Property
 
        Private _Visible As Boolean
        Public ReadOnly Property Visible() As Boolean
            Get
                Return _Visible
            End Get
        End Property
 
        Private _DisplayIndex As Integer
        Public ReadOnly Property DisplayIndex() As Integer
            Get
                Return _DisplayIndex
            End Get
        End Property
 
    End Class

When I try to use it, I cannot seem to use named parameters:


Huh?

Well, I thought, perhaps Attributes don't support named parameters. I know they can behave a little weird (they don't support all types in their arguments for example I think), so I thought little of it.

But then... I noticed something else. If you take a look at my code of the attribute class again. Notice that I am using an attribute on that class as well... And what do you know: named parameters. Working just fine... The AttributeUsage attribute has the exact same configuration: one fixed parameter and two optional parameters. I seem to be able to call them using named parameters just fine, where I cannot call my own attribute constructor with named parameters...

What's going on... Am I losing my mind? Is VS bugged? Or is it infected with a demon?