code: def additional_properties!(addprops)
        @nbuild[NS_EWS_TYPES].AdditionalProperties {
          addprops.each_pair {|k,v|
            dispatch_field_uri!({k => v}, NS_EWS_TYPES)
          }
        }
      end
docs: Build the AdditionalProperties element
   @see http://msdn.microsoft.com/en-us/library/aa563810.aspx