xml file creation from return type is list methods

Question

Hi All,
I am developing product using asp.net c sharp.I have method name is public List<Role> GetRoles(int UserId) and this method return list of Roles which is assigned user. I need to write or create xml file for user Roles to build menu control from xml file.

That means,
1.How to write list of Roles in xml file from returning list of Roles by this method?
2.How to build menu control from xml file?

Thanks,