Filtering EntityCollection type field by filter descriptor in VB.NET

[Atul]

I have a QueryableCollectionView which is bind with the entity and the entity has a child entity collection. I am filtering this queryable collection by creating filter descriptors and adding them to the collections.
            For string and boolean field it is very easy to create a filter descriptor like this:

 Dim FolderIDFD As New FilterDescriptor
            FolderIDFD.Member = "FolderID"
            FolderIDFD.Operator = FilterOperator.IsEqualTo
            FolderIDFD.Value = SelectedUserFolder.Id
            MediaCollectionView.FilterDescriptors.Add(FolderIDFD)

But for filtering an entitycollection field how can be this possible?

i want to filter a field which child of child of the collection, for this first i have to ensure that the child entity collection should not be nothing
in first condition.
Than how can i implement the filter descriptor for an EntityCollection field?

I have also used

Dim UnProfiledFD As New FilterDescriptor
        UnProfiledFD.Member = "TaggedMediums"
        UnProfiledFD.Operator = FilterOperator.IsNotNull

        MediaCollectionView.FilterDescriptors.Add(UnProfiledFD)

but it is not working for entityCollection field.

[Atul]

Here i am able to filter my child entity collection by IsNull and also IsNotNull conditions :

Dim FolderIDFD As New FilterDescriptor
        FolderIDFD.Member = "TaggedMediums"
        FolderIDFD.Operator = FilterOperator.IsNotNull
        MediaCollectionView.FilterDescriptors.Add(FolderIDFD)

     But also able to filter the entity collection field by this:

Dim FolderIDFD As New FilterDescriptor
        FolderIDFD.Member = "TaggedMediums.Count"
        FolderIDFD.Operator = FilterOperator.IsGreaterThan
        FolderIDFD.Value = 0
        MediaCollectionView.FilterDescriptors.Add(FolderIDFD)

   Can you help me to filter the child collection from its field like  "TaggedMediums.TagID"
That means i want to filter the collection by the child entity collection's field i.e. TagID, can i use "CreateFilterExpression" for this type of filtration.
           If it is possible then help me to do this by showing an example for filtering via "CreateFilterExpression".