How to get outlook recurrence appointment?

How to get outlook recurrence appointment?

I user webdav to get outlook appointment,It works well, but now,I find it not
get recurrence appointment,my strQyery is 


 strQuery = "<?xml version=\"1.0\"?>"
                 + "<g:searchrequest
xmlns:g=\"DAV:\">"
                 + "<g:sql>SELECT
\"urn:schemas:calendar:location\",
\"urn:schemas:httpmail:subject\", "
                 + "\"urn:schemas:calendar:dtstart\",
\"urn:schemas:calendar:dtend\", "
                 + "\"urn:schemas:calendar:busystatus\",
\"urn:schemas:calendar:instancetype\" "
                 + "FROM Scope('SHALLOW TRAVERSAL OF \"" +
strCalendarURI + "\"') "
         + "WHERE NOT \"urn:schemas:calendar:instancetype\" = 1
"


       + " where \"DAV:contentclass\" =
'urn:content-classes:appointment' "
 
      + "ORDER BY \"urn:schemas:calendar:dtstart\" ASC"
                 + "</g:sql></g:searchrequest>";

 

at MSDN, it say instancetype is appointment type, but,no matter I change its
value, It still not read recurrence appoint

I solve the problem,set WHERE NOT
\"urn:schemas:calendar:instancetype\" = 5  and also set      "AND
\"urn:schemas:calendar:dtend\" > '" + dt + "' " is
ok