c# - Calculate 2 dataGridView and Update an SQL Data Table -

i have 2 datatables table_1 , table_2. what's wrong code? can't add in table_2 sum of stock table_1?

when update once, have correct output.

http://tinypic.com/view.php?pic=1632bs&s=5

when press update button once more, updates first row, shown in following pic:

http://tinypic.com/r/350p6hd/5

private void txtid_textchanged(object sender, eventargs e)     {         sqlconnection csq = new sqlconnection("workstation id=;initial catalog=iridadb; integrated security=sspi");          sqldataadapter dsaq = new sqldataadapter();         dataset dsq = new dataset();          dsaq.selectcommand = new sqlcommand("select * table_1 left(id, " + txtid.text.length + ") = '" + txtid.text + "' order itemid asc", csq);         dsq.clear();          dsaq.fill(dsq);          datagridview1.datasource = dsq.tables[0];         datagridview1.allowusertoaddrows = false;          binddatagridview2();     }      public void binddatagridview2()     {          sqlconnection csq = new sqlconnection("workstation id=;initial catalog=iridadb; integrated security=sspi");          sqldataadapter dsaq = new sqldataadapter();         dataset dsq = new dataset();          dsaq.selectcommand = new sqlcommand("select * table_2 ", csq);         dsq.clear();          dsaq.fill(dsq);          datagridview2.datasource = dsq.tables[0];         datagridview2.allowusertoaddrows = false;      }      private void btnupdate_click(object sender, eventargs e)     {         (int = 0; <= datagridview1.rows.count - 1; i++)         {             if (!datagridview1.rows[i].isnewrow)             {                   sqlconnection connan = new sqlconnection("data source=;initial catalog=iridadb; integrated security=sspi");                 sqldataadapter danan = new sqldataadapter();                 danan.updatecommand = new sqlcommand("update  table_2 set stock  = @stock  itemid = @itemid", connan);                 danan.updatecommand.parameters.add("@itemid", sqldbtype.varchar).value = convert.tostring(datagridview1.rows[i].cells[1].value).tostring();                  danan.updatecommand.parameters.add("@stock", sqldbtype.varchar).value = (double.parse(datagridview1.rows[i].cells[2].value.tostring()) + double.parse(datagridview2.rows[i].cells[1].value.tostring())).tostring();                    connan.open();                 danan.updatecommand.executenonquery();                 connan.close();                  binddatagridview2();               }         }     } 

check calculations of sum:

(double.parse(datagridview1.rows[i].cells[2].value.tostring()) + double.parse(datagridview2.rows[i].cells[1].value.tostring())).tostring(); 

you calculating sum of rows same rowindex, updating database itemid

when in looping index i = 2 count stock(where itemid = 03) + stock(where itemid = 02) -> stock of item 02 not updating stay on 100. thats why item 03 stock 100 + 1

because total stock in database already, use query this

update  table_2 set  stock = cast(         cast(stock decimal(19,4)) + cast(@stock decimal(19,4))          varchar(max))  itemid = @itemid" 

and take values datagridview1

danan.updatecommand.parameters.add("@itemid", sqldbtype.varchar).value = convert.tostring(datagridview1.rows[i].cells[1].value).tostring();  //  danan.updatecommand.parameters.add("@stock", sqldbtype.varchar).value = (double.parse(datagridview1.rows[i].cells[2].value.tostring()) 

p.s. sorry, seems strangely, when stored values of double/decimal varchar ...?