Question

The easiest way to explain this problem is to show you some code:

Public Interface IAmAnnoyed
End Interface

Public Class IAmAnnoyedCollection
    Inherits ObjectModel.Collection(Of IAmAnnoyed)
End Class

Public Class Anger
    Implements IAmAnnoyed
End Class

Public Class MyButton
    Inherits Button

Private _Annoyance As IAmAnnoyedCollection
<DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _
Public ReadOnly Property Annoyance() As IAmAnnoyedCollection
    Get
        Return _Annoyance
    End Get
End Property

Private _InternalAnger As Anger
<DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _
Public ReadOnly Property InternalAnger() As Anger
    Get
        Return Me._InternalAnger
    End Get
End Property

Public Sub New()
    Me._Annoyance = New IAmAnnoyedCollection
    Me._InternalAnger = New Anger
    Me._Annoyance.Add(Me._InternalAnger)
End Sub

End Class

And this is the code that the designer generates:

Private Sub InitializeComponent()
    Dim Anger1 As Anger = New Anger
    Me.MyButton1 = New MyButton
    '
    'MyButton1
    '
    Me.MyButton1.Annoyance.Add(Anger1)
    // Should be: Me.MyButton1.Annoyance.Add(Me.MyButton1.InternalAnger)
    '
    'Form1
    '
    Me.Controls.Add(Me.MyButton1)

End Sub

I’ve added a comment to the above to show how the code should have been generated. Now, if I dispense with the interface and just have a collection of Anger, then it persists correctly.

Any ideas?

Update 1

I’m sick of this. This problem was specifically about persisting an interface collection but now on further testing it doesn’t work for a normal collection. Here’s some even simpler code:

Public Class Anger
End Class

Public Class MyButton
    Inherits Button

Private _Annoyance As List(Of Anger)
<DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _
Public ReadOnly Property Annoyance() As List(Of Anger)
    Get
        Return _Annoyance
    End Get
End Property

Private _InternalAnger As Anger
<DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _
Public ReadOnly Property InternalAnger() As Anger
    Get
        Return Me._InternalAnger
    End Get
End Property

Public Sub New()
    Me._Annoyance = New List(Of Anger)
    Me._InternalAnger = New Anger
    Me._Annoyance.Add(Me._InternalAnger)
End Sub

End Class

The designer screws up the persistence code in the same way as the original problem.

Update 2

I’ve worked out what is going on. I wondered why sometimes it would work and not others. It boils down to the name that I give to the internal property and the collection.

If I rename the property ‘Annoyance’ to ‘WTF’, it will serialize correctly because ‘WTF’ is, alphabetically, after the name of the collection – ‘InternalAnger’.

It looks like the serializer is creating instances of objects alphabetically and needs my internal property to be created by the time it comes to create the collection.

I can fix this with a rename, but that’s a hack and I fear that writing a custom serializer is a big job – which I’ve never done before.

Any ideas?

Update 3

I’ve answered the question with a hack. I’m fairly confident in it unless MS change the way that codedom serializers the designer code.

Answer 1

As i said in the OP, the problem boils down to the name that I give to the internal property and the collection.

Without delving into a custom codedom serializer, the simple solution is to make sure the internal property’s name is alphabetically before any other property that will reference it.

I do this by retaining the original property name ‘InternalProperty’, but I disable serialization and refer it to a proxy property, that is cunningly named, and is serialized.

Private _InternalProperty
Public ReadOnly Property InternalProperty
    Get
        Return Me._ProxyInternalProperty 
    End Get
End Property

<Browsable(False), EditorBrowsable(Never), DesignerSerializationVisibility(Content)> _
Public ReadOnly Property _ProxyInternalProperty
    Get
        Return Me._InternalProperty
    End Get
End Property

This is a hack, but its better than renaming my property AInternalProperty. Also, the user will never see _ProxyInternalProperty because it’s hidden, and even if they did discover it, there is no danger in referencing it.