Combine node attribute and child attributes together

[Tarff]

Basically I have\[code\]<?xml version="1.0" encoding="utf-8"?><A> <B key="1"> <Hash value="http://stackoverflow.com/questions/14467073/SHA256" /> <Hash value="http://stackoverflow.com/questions/14467073/MD5" /> </B> <B key="2"> <Hash value="http://stackoverflow.com/questions/14467073/SHA512" /> <Hash value="http://stackoverflow.com/questions/14467073/SHA1" /> </B><B key="3"> <Hash value="http://stackoverflow.com/questions/14467073/bcrypt" /> </B>......</A>\[/code\]I want to get pairs with key and value. The key is the attribute value of node B, the value is the combination of node Hash's attribute values.For example:\[code\]{1,SHA256+MD5};{2,SHA512+SHA1};{3,bcrypt};\[/code\]Thanks