How do I group employees by their office on a vb.net page?

I have a query that returns a list of employees, and the office they work in.  Instead of listing the employees in alphabetical order, I need to list them in alphabetical order by Office.  How do I "filter thru" my list and display employees grouped by office, wiithout doing separate queries for each office?  Here's what I need to do

Chicago
   Employee1
   Employee2
   Employee3

New York
  Employee 4
  Employee 5

Washington D.C.
  Employee 6
  Employee 7

 All I can get my list to do is list employee 1-7 and their office name beside the employee name.  I don't know how to do this grouping...

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