What's wrong with my RowUpdating function?

[anniebai]

Please help me with this RowUpdating function.
I copied it from the internet and modified the part that I could understand. and not surprisingly, it's not working.
When I tried to update a row, there's not error message, it's just not updating anything.

protected void gvStudentsAndProjects_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        GridView gv = (GridView)sender;
        for (int i = 0; i < gv.Columns.Count; i++)
        {
            DataControlFieldCell cell = gv.Rows[e.RowIndex].Cells[i] as DataControlFieldCell;
            gv.Columns[i].ExtractValuesFromCell(e.NewValues, cell, DataControlRowState.Edit, true);
        }
        //e.Cancel = true;
        databind();
    }