SQL Server Gridview checkbox value not getting updated in Database in RowUpdating event

 bool isChecked = ((CheckBox)Gridview1.Rows[e.RowIndex].Cells[e.RowIndex].Controls[0]).Checked;

            if (isChecked)

            { chk = 1; }

            else

            {  chk = 0; }

                cmd.Parameters.Add("@check", SqlDbType.Int).Value = chk;

in the above code if i unslect the check box i get ischecked value=false

& chk value=0 but on updating in sql tbl the value does not chnage