Xml in C#

Question

If I have a XML-document like his: ---- -------- ------------- Test ------------- 24 --------- ---- ---- --------- -------------- Test2 -------------- 19 --------- ---- ---- --------- ---------------- Test3 ---------------- 33 --------- ---- How can I add a street in "Paris"? Is it possible or is it to difficult? Thx in advance!