关于xml：将XmlNodeList加载到XmlDocument中而不循环？

Private Function GetPreviousMonthsXml(ByVal months As Integer, ByVal startDate As Date, ByVal xDoc As XmlDocument, ByVal path As String, ByVal nodeName As String) As XmlDocument
    '' build xpath string with list of months to return
    Dim xp As New StringBuilder("//")
    xp.Append(nodeName)
    xp.Append("[")
    For i As Integer = 0 To (months - 1)
      '' get year and month portion of date for datestring
      xp.Append("starts-with(@Id, '")
      xp.Append(startDate.AddMonths(-i).ToString("yyyy-MM"))
      If i < (months - 1) Then
       xp.Append("') or")
     Else
       xp.Append("')]")
     End If
   Next

   '' *** This is the block that needs to be refactored ***
   '' import nodelist into an xmldocument
   Dim xnl As XmlNodeList = xDoc.SelectNodes(xp.ToString())
   Dim returnXDoc As New XmlDocument(xDoc.NameTable)
   returnXDoc = xDoc.Clone()
   Dim nodeParents As XmlNodeList = returnXDoc.SelectNodes(path)
   For Each nodeParent As XmlNode In nodeParents
     For Each nodeToDelete As XmlNode In nodeParent.SelectNodes(nodeName)
       nodeParent.RemoveChild(nodeToDelete)
     Next
   Next

   For Each node As XmlNode In xnl
     Dim newNode As XmlNode = returnXDoc.ImportNode(node, True)
     returnXDoc.DocumentElement.SelectSingleNode("//" & node.ParentNode.Name &"[@Id='" & newNode.Attributes("Id").Value.Split("-")(0) &"']").AppendChild(newNode)
   Next

   '' *** end ***
   Return returnXDoc
End Function

Dim returnXDoc As New XmlDocument(xDoc.NameTable)
returnXDoc = xDoc.Clone()

Dim returnXDoc As XmlDocument = xDoc.Clone()