update qty datagrid in c# and mysql

Question

I have a C# application with a datagrid in windows form. I need to update my qty from 0 to 500 and update to my database. however I got messagebox that says "

you have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '50 where pcode like 'ph003'" at line 1

public void LoadStockIn()
    {
        int i = 0;
        dataGridView2.Rows.Clear();
        con.conDB.Open();
        cmd = new MySqlCommand("SELECT * FROM vwstockin where refno like '" + txtrefno.Text + "' and status like 'Pending'", con.conDB);
        dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            i++;
            dataGridView2.Rows.Add(i, dr[0].ToString(), dr[1].ToString(), dr[2].ToString(), dr[3].ToString(), dr[4].ToString(), dr[5].ToString(), dr[6].ToString());
        }
        dr.Close();
        con.conDB.Close();
    }

 private void savebtn_Click(object sender, EventArgs e)
    {
        try
        {
            if(dataGridView2.Rows.Count > 0 )
            {
                if (MessageBox.Show("Are you sure you want to save this records?", stitle, MessageBoxButtons.YesNo,  MessageBoxIcon.Question)== DialogResult.Yes)
                { 
                    for (int i =0; i< dataGridView2.Rows.Count; i++)
                    {
                        //Update product qty
                        con.conDB.Open();
                        cmd = new MySqlCommand("Update tblproduct set qty = qty " + int.Parse(dataGridView2.Rows[i].Cells[5].Value.ToString()) +" WHERE pcode like '" +dataGridView2.Rows[i].Cells[3].Value.ToString() + "'",con.conDB);
                        cmd.ExecuteNonQuery();
                        con.conDB.Close();

                        //updatet tblstock qty
                        con.conDB.Open();
                        cmd = new MySqlCommand("update tblstock set qty = qty + " + int.Parse(dataGridView2.Rows[i].Cells[5].Value.ToString()) + ", status = 'Done' where id like '" + dataGridView2.Rows[i].Cells[1].Value.ToString() + "'",con.conDB);
                        cmd.ExecuteNonQuery();
                        con.conDB.Close();
                    }
                    Clear();
                    LoadStockIn();
                }
            }
        }
        catch(Exception ex)
        {
            con.conDB.Close();
            MessageBox.Show(ex.Message, stitle);
        }
    }

Answer 1

This is culprit qty = qty " + int.Parse(dataGridView2.Rows[i].Cells[5].Value.ToString()) +" . It should be qty = int.Parse(dataGridView2.Rows[i].Cells[5].Value.ToString()) +" .

Basically you have int datatype for this column. and you are providing wrong value. Make set qty = " + and it will work.