why optionDataSource not get refresh?

[turtledove]

i am using SelectItem from smartgwt 2.2, like this:

templateItem = new SelectItem("template", "XXXX");
templateItem.setOptionDataSource(BasicOptionDataSource.getInstance());
templateItem.setValueField("value");
templateItem.setDisplayField("display");


when data of BasicOptionDataSource get updated, through RPC insteadof DataSource operation. templateItem's valuemap is not get updated, unless i refresh the browser. i found that no matter how many times i execute above codes, the server-side only get executed once.

even i call BasicOptionDataSource.getInstance().invalidateCache(); manually, the value map of SelectItem still not get updated.

is there any mothed works like ListGrid.invalidateCache() in SelectItem?
how can i get my code works?
thanks!