Save Node to another file xml Windows phone 7

[mad142]

I have a XML file:\[code\]<Root> <Lv1> <1_Data_Lv2_1>A1</1_Data_Lv2_1> <2_Data_Lv2_1>A2</2_Data_Lv2_1> </Lv1> <Lv1> <1_Data_Lv2_1>B1</1_Data_Lv2_1> <2_Data_Lv2_1>B2</2_Data_Lv2_1> </Lv1></Root>\[/code\]C#\[code\]using (var myStream = new IsolatedStorageFileStream("Settings.xml", FileMode.Open, myIsolatedStorage)){ xdoc = XDocument.Load(myStream);} var lv1s = from lv1 in xdoc.Elements("Root") select new { Children = lv1.Descendants("Lv1") };foreach (var lv1 in lv1s){ foreach (var lv2 in lv1.Children) { MessageBox.Show(Convert.ToString(lv2.Value)); }}\[/code\]How can i get All Node lv1 of <1_Data_Lv2_1> == "A1" and write to another xml?