changing DataViewManager.RowFilter in DataGrid

Question

Hi, when I use DataView in a DataGird, whenever I change the RowFilter, grid shows the matched data. but when I use DataViewManager, the first time that I use "SetDataBinding" it shows the matched data, later when I change the filter, it doesn't effect on grid. how should I let grid knows that the filter has been changed? why in DataView it works fine but not in DataViewManager? thanks