WEBカスタムコントロールにデザイン時でも設定可能なString配列型のプロパティを作成したい

' コレクションメンバクラス
<ToolboxData("<{0}:MyString></{0}:MyString>")> _
Public Class MyString
    Public Sub New()
    End Sub

    Public Property [Value]() As String
    End Property
End Class

' コレクション
<DefaultProperty("Item")> _
Public Class MyStringCollection
    Implements IList

    <PersistenceMode(PersistenceMode.InnerProperty)> _
    Default Public Overridable ReadOnly Property Item(ByVal Index As Integer) As MyString
        Get
            Return CType(IList_Item(Index), MyString)
        End Get
    End Property

    Private Property IList_Item(ByVal Index As Integer) As Object Implements IList.Item
    End Property
End Class

' コントロール
Public Class MyControl
    Inherits WebControl

    <PersistenceMode(PersistenceMode.InnerDefaultProperty)> _
    Public ReadOnly Property MyStrings() As MyStringCollection
    End Property
End Class

引用
Public Class ExTextBox
	Inherits System.Web.UI.WebControls.TextBox

	Dim _DataColumnName As String()
	Public Property DataColumnName() As String()
		Get 
			Return Me._DataColumnName
		End Get 
		Set(ByVal Value As String())
			Me._DataColumnName = Value
		End Set
	End Property

	Public Sub New()

	End Sub
...
End Sub

Public Class ExTextBox 
	Inherits System.Web.UI.WebControls.TextBox 

	Dim _DataColumnName As StringCollection
	Public Property DataColumnName() As StringCollection
		Get 
			Return Me._DataColumnName
		End Get 
		Set(ByVal Value As StringCollection)
			Me._DataColumnName = Value
		End Set
	End Property

	Public Sub New()

	End Sub
...
End Sub

	Public Sub New()
		' 引数はなかったかな？調べてね
		_DataColumnName = New StringCollection()
	End Sub

Public Class ExTextBox
    Inherits System.Web.UI.WebControls.TextBox

    Private _DataColumnName As String()

    <TypeConverter(GetType(MyStringConverter))> _
    Public Property DataColumnName() As String()
        Get
            Return _DataColumnName
        End Get
        Set(ByVal Value As String())
            _DataColumnName = Value
        End Set
    End Property

End Class

'String 配列 コンバータ
Public Class MyStringConverter
    Inherits StringConverter

    Public Overloads Overrides Function ConvertTo(ByVal context As ITypeDescriptorContext, _
                                                  ByVal culture As Globalization.CultureInfo, _
                                                  ByVal value As Object, _
                                                  ByVal destinationType As Type) As Object
        If (destinationType Is GetType(String)) AndAlso (TypeOf value Is String()) Then
            Return String.Join(Chr(&H7F).ToString(), CType(value, String()))
        Else
            Return MyBase.ConvertTo(context, culture, value, destinationType)
        End If
    End Function

    Public Overloads Overrides Function ConvertFrom(ByVal context As ITypeDescriptorContext, _
                                                    ByVal culture As Globalization.CultureInfo, _
                                                    ByVal value As Object) As Object
        If (TypeOf value Is String) Then
            Return CType(value, String).Split(New Char() {Chr(&H7F)})
        Else
            Return MyBase.ConvertFrom(context, culture, value)
        End If
    End Function

End Class