<dx:ASPxGridViewExporter ID="gridExport" GridViewID="grdDevGridID" runat="server"></dx:ASPxGridViewExporter>
Print Button Click event
//before export want to rebind Gridview again.
grdDevGridID.Datasource =Datatable;
grdDevGridID.Databind() ;
gridExport.WriteXlsxToResponse();