Has anyone figured out how to generate a xml stream to a column in a dataset instead of to a file?

I am saving treeview information to an xml document and do to customer contraints, I need to save the xml to a column in a dataset and be able to read it back to recreate the treeview.

I am using the following code in VB.Net to accomplish part of the process although it only writes to a file.

        Dim formatter As SoapFormatter = New SoapFormatter()
        Dim stream As Stream = New FileStream("c:\Free.xml", FileMode.Create, FileAccess.Write, FileShare.None)

        Dim root As New TreeNode()
        Dim node As TreeNode
        For Each node In treForceStructure.Nodes
            root.Nodes.Add(CType(node.Clone(), TreeNode))
        Next node
        formatter.Serialize(stream, root)
        stream.Close()

Any ideas on how to accomplish this? I can't seem to find any info on it.

Thanks,
Pat.