or
grid.collapseGroup(grid.tbody.find(">tr.k-grouping-row")); to a grouping event?
$("#dropdownbox").kendoDropDownList({ dataSource: new kendo.data.DataSource({ dataTextField: "name", dataValueField: "id", transport: { read: { url: "WebService.asmx/GetDates", data: { startDate: "2010/10/20", endDate: "2012/10/20" } } }, schema: { type: "xml", data: "NewDataSet/dates", model: { fields: { building_name: "name/text()", building_id: "id/text()" } } } }) });<NewDataSet> <dates> <id>4</id> <name>TestItem1</name> </dates> <dates> <id>5</id> <name>TestItem2</name> </dates></NewDataSet>