当我想编辑股票时，它会添加新项目

Question

我想做一个代码，如果brcode是相同的，那么将添加商品库存而不是添加新商品，但我总是最终添加库存并添加新商品。我只想要添加股票......

这是代码。

private void btnadd_Click(object sender, EventArgs e)
    {
        foreach  (DataGridViewRow row in dataGridView1.Rows)
        {
            if (Convert.ToString(row.Cells[3].Value) == codeadd.Text)
            {
                DialogResult dialogResult = MessageBox.Show("an Item with BrCode already exists. Do you with to add to the stock?", "Item Manager", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                if (dialogResult == DialogResult.Yes)
                {
                    int addedstock = (Convert.ToInt32(row.Cells[4].Value) + Convert.ToInt32(stockadd.Text));
                    cmd = new SqlCommand("UPDATE Products SET Item_Stock = @Stock WHERE Item_Code=@Item_Code", con);                        
                    cmd.Parameters.Add(new SqlParameter("@Stock", addedstock));
                    cmd.Parameters.Add(new SqlParameter("@Item_Code", codeadd.Text));

                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                    dt.Clear();
                    sda = new SqlDataAdapter("Select * From Products", con);
                    dt = new DataTable();
                    sda.Fill(dt);
                    dataGridView1.DataSource = dt;
                }
            }
            else
            {
                cmd = new SqlCommand("INSERT INTO Products Values(@Item_Name, @Item_Price, @Item_Code, @Item_Stock, @Item_ExpDate)", con);
                SqlParameter[] param = new SqlParameter[5];

                param[0] = new SqlParameter("@Item_Name", SqlDbType.VarChar, 50);
                param[0].Value = nameadd.Text;

                param[1] = new SqlParameter("@Item_Price", SqlDbType.VarChar, 50);
                param[1].Value = priceadd.Text;

                param[2] = new SqlParameter("@Item_Code", SqlDbType.VarChar, 50);
                param[2].Value = codeadd.Text;

                param[3] = new SqlParameter("@Item_Stock", SqlDbType.Int);
                param[3].Value = Convert.ToInt32(stockadd.Text);

                param[4] = new SqlParameter("@Item_ExpDate", SqlDbType.DateTime);
                param[4].Value = expdateadd.Text;

                con.Open();
                cmd.Parameters.AddRange(param);
                cmd.ExecuteNonQuery();
                con.Close();
                dt.Clear();
                sda = new SqlDataAdapter("Select * From Products", con);
                sda.Fill(dt);
                dataGridView1.DataSource = dt;
            }

谢谢