How to make an asp.net page to return a JSON or XML

 I don't want to use a WebService, unless there isn't any alternate method for doing this:
I want to query a database and return results (i.e. record-set) to a client via Ajax, so I would like to get the results, convert them to a JSON or XML format and send it to a client.
 Is there a way how to accomplish this?
 
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