Custom Control with Custom Collection Property

I have an ASPX Custom Control which is supposed to load it's prop开发者_JAVA百科erties into an internal collection (defined with PersistenceMode.InnerProperty). Here's the ASPX

<cc:CustomControl runat="server">
    <Queries>
        <cc:QueryTypeOne ... />
    </Queries>
</cc:CustomControl>

The problem is, when I use the above code, I get a parser error "Type 'CustomControls.QueryCollection' does not have a public property named 'QueryTypeOne'". (FYI QueryTypeOne inherits a class called Query). I don't want a public property called QueryTypeOne, I want it to load into the QueryCollection property I have waiting for it!

Here's all the relevant code.

CustomControls.CustomControl class has a property called queries

<DefaultValue(CType(Nothing, String)),
     MergableProperty(False),
     PersistenceMode(PersistenceMode.InnerProperty)> _
    Public Property Queries As QueriesContainerTag

And QueriesContainerTag just exists to allow the ASPX engine to get access to the collection (QueryCollection)

<ParseChildren(True, "Queries"),
 Serializable()> _
Public Class QueriesContainerTag
    Private _Queries As QueryCollection = Nothing
    Public ReadOnly Property Queries As QueryCollection
        Get
            If _Queries Is Nothing Then
                _Queries = New QueryCollection()
            End If

            Return _Queries
        End Get
    End Property
End Class

Where QueryCollection is a custom class that implements ICollection with this signature:

Public Class QueryCollection
    Implements IList(Of Query), ICollection(Of Query), IEnumerable(Of Query)

Also, oddly enough, if I changed QueriesContainerTag to use a built in list class, everything works perfectly!

<ParseChildren(True, "Queries"),
 Serializable()> _
Public Class QueriesContainerTag
    Private _Queries As List(Of Query) = Nothing
    Public ReadOnly Property Queries As List(Of Query)
        Get
            If _Queries Is Nothing Then
                _Queries = New List(Of Query)()
            End If

            Return _Queries
        End Get
    End Property
End Class

Microsoft does not implement Generic List support for custom control collection properties! As soon as I added the IList interface, everything started working exactly as expected.

Personally, I don't understand why they did this. Even more, I would have thought an IList(Of T) (IList<T> for you C# guys) should work automatically everywhere an IList is required. After all, T will always inherit from object.