arcgis 查询 group by order by

IQueryDef2 queryDef2 = (IQueryDef2)featureWorkspace.CreateQueryDef();

// Specify the table and fields to query.
queryDef2.Tables = "Cities";
queryDef2.SubFields = "Name, Pop1996";
queryDef2.PostfixClause = "ORDER BY Pop1996 DESC";


// Execute the query.using(ComReleaser comReleaser = new ComReleaser())
{
    ICursor cursor = queryDef2.Evaluate2(true);
    comReleaser.ManageLifetime(cursor);
    int nameIndex = cursor.FindField("Name");
    int pop1996Index = cursor.FindField("Pop1996");
    IRow row = null;
    while ((row = cursor.NextRow()) != null)
    {
        String cityName = Convert.ToString(row.get_Value(nameIndex));
        int population = Convert.ToInt32(row.get_Value(pop1996Index));
        Console.WriteLine("{0}: {1}", cityName, population);
    }
}