Problem deriving from ToolboxItemAttribute in .Net, Winforms

As an example, here's a simple attribute, derived from ToolboxItemAttribute:

<ToolboxItemX(False)> _
Public Class Class1
    Inherits Button
End Class

Public Class ToolboxItemXAttribute
    Inherits ToolboxItemAttribute

    Public Sub New(ByVal defaultType As Boolean)
        MyBase.New(defaultType)
    End Sub

End Class

The problem is that when I show the toolbox, Class1 is appearing in it. It's as if my attribute is ignored, and so the default toolboxitem attribute is used.

I've used reflector to 开发者_JAVA百科look at the logic of ToolboxService.GetToolboxItem and as far as I can see, it should pick up my attribute and see that the item should not be displayed in the toolbox.

PS: I've tried resetting the toolbox, closing the ide and reopening etc.

---

The Windows Forms toolbox is remarkably cranky. This ought to work, but indeed doesn't. No idea why, this code is locked up inside Visual Studio. As a workaround, you can hide it by using the DesignTimeVisibleAttribute. Like this:

<ToolboxItemX(False)> _
<DesignTimeVisible(False)> _
Public Class Class1
    Inherits Button
End Class