Unable to Create CollectionView Source to Group and Filter

I'm unable to Create CollectionViewSource with the Collection,I have an XML file and Deserilized it to get Collection,

XML File

<?xml version="1.0" encoding="utf-8" ?>
<Stacks>

<Stack Id="001" Name="KEYABLE">
  <Pages PageName="Stack1">
    <Page PT="ENVELOPE" >
      <Files>
        <File FN="C:\Work\002885118s51128444038\PageCode\X11090_0009_001\X11090_0009_001_001.tif" FF="TIFF" Index="1"/>
      </Files>
    </Page>
    <Page PT="UNKNOWN">
      <Files>
        <File FN="C:\Work\002885118s51128444038\PageCode\X11090_0009_001\X11090_0009_001_001.tif" FF="TIFF" Index="2"/>
      </Files>
    </Page>
        </Pages>
</Stack>

<Stack Id="002" Name="KEYABLE">
  <Pages PageName="Stack2">
    <Page PT="ENVELOPE">
      <Files>
        <File FN="C:\Work\002885118s51128444038\PageCode\X11090_0009_001\X11090_0009_001_003.tif" FF="TIFF" Index="1"/>
      </Files>
    </Page>
    <Page PT="UNKNOWN">
      <Files>
        <File FN="C:\Work\00288511851128436351\N12208_0000_020\00000059.tif" FF="TIFF" Index="2"/>
      </Files>
    </Page>
     </Pages>
  </Stack>

</Stacks>

Public Sub New()
            InitializeComponent()
            Dim Reader As New Xml.XmlTextReader("F:\WPFSample Apps\TabControl--DynamicTab\WPFDyanamicTab_vb\XMLFile.xml")
            Dim oStack As New Stacks
            oStack = Sympraxis.Capture.Common.XObjectBase.OpenXml(Reader, oStack.GetType)

            Me.DataContext = oStack
    Dim myCollectionView As ListCollectionView
            myCollectionView = CType(CollectionViewSource.GetDefaultView(Me.DataContext), ListCollectionView)

        End Sub

Quote:

This is a collection contains List of Collections.