Combining xmlnodes from 2 different xml's

[lazd]

I have a class with 2 string fields, both of them will hold an XML, which are entirely different, I mean different root nodes or some reason I have to append these XMLs.\[code\]public class someclass { public string carsxml {get;set;} public string bikesxml {get;set;}}\[/code\]cars xml will be like \[code\]<cars> <car> <company>honda</company> <cost>10000</cost> </car></cars>\[/code\]bikesxml will be like \[code\]<bikes> <bike> <model>2012</model> <cost>33333</cost> </bike></bikes>\[/code\]How do I append these 2 XMLs in to a single XML?