How to Access Custom Section from App.config

My app.config is,

<sectionGroup name="CategorySettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" ><section name="WindowsService.CategoryAttributeSettings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" /></sectionGroup>

AND this is declared as

<CategorySettings><WindowsService.CategoryAttributeSettings>      <category categoryname="Document_Level" required="true"><number dataType="text" required="true">Document Number</number></category></WindowsService.CategoryAttributeSettings></CategorySettings>

Please let me know how do I read all category values dynamically wherecategoryname="Document_Level"?

This is really urgent.

Thanks, 

AC