Reading/Sorting/Searching XML File

Question

I need to read in a XML file that has three tags I am concerned with, we will call them A, B and C. A and C are both strings and B is an int (number). Once the XML file is read in I need to check to make sure that there are no duplicates of B and no duplicates of A. I am assuming on read in it would need to be put into an array and sorted then each value searched to make sure it doesn't already exist? Just not sure on the code behind how to do this...??? Any help would be great.. Thanks!