SQLDatasource查询更改后，GridView Row没有更新？

I have a grid view and i have bonded sql data source to that. on page i have drop down, as soon as selected value of drop down get changes, i change the select query of sql data source and again binding the data to grid view. before doing this if i update the grid view row its get updated but after doing previous process my update is not working. it don't show me any error. it don't take edited values.I have a grid view and i have bonded sql data s