XElement xmlTree1 = new XElement("Root",
new XElement("Child1", 1),
new XElement("Child2", 2),
new XElement("Child3", 3),
new XElement("Child4", 4),
new XElement("Child5", 5),
new XElement("Child6", 6)
);
XElement xmlTree2 = new XElement("Root",
from el in xmlTree1.Elements()
where((int)el >= 3 && (int)el <= 5)
select el
);
Console.WriteLine(xmlTree2);