[c#] Looping each row in datagridview

How to loop each row that readed? in my code, the row won't bind to next row because of the same productID, so the datagridview won't move to new row, it still in the same row and overwrite the price (for some product, i have two price). How to loop it to show the same productID but it have different price.

EX : 1 Hamburger have 2 price Hamburger : $1 and $2 when i get the data with looping it, the resould shoult be have 2 Row with same product but different price. How to do this? below is my code

productID = odr["product_id"].ToString();
quantity = Double.Parse(odr["quantity"].ToString());

//processing data...
key = productID.ToString();

if (key != key_tmp)
{
    //update index...
    i++;

    //updating variable(s)...
    key_tmp = key;
}

if (datagridviews.Rows[i].Cells["qty"].Value != null) //already has value...
{
    currJlh = Double.Parse(ddatagridviews.Rows[i].Cells["qty"].Value.ToString());
}
else //not yet has value...
{
    currQty = 0;
}
currQty += qty;

//show data...
datagridviews.Rows[i].Cells["price"].Value = cv.toAccountingCurrency_en(Double.Parse(odr["item_price"].ToString()));
MessageBoxes.Show(i.ToString());
MessageBoxes.Show(datagridviews.Rows[i].Cells["price"].Value.ToString()); // in here there is two price that looped but won't showed in datagridviews

help me out :)

I used the solution below to export all datagrid values to a text file, rather than using the column names you can use the column index instead.

foreach (DataGridViewRow row in xxxCsvDG.Rows)
{
    File.AppendAllText(csvLocation, row.Cells[0].Value + "," + row.Cells[1].Value + "," + row.Cells[2].Value + "," + row.Cells[3].Value + Environment.NewLine);
}

Best aproach for me was:

  private void grid_receptie_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
    {
        int X = 1;
        foreach(DataGridViewRow row in grid_receptie.Rows)
        {
            row.Cells["NR_CRT"].Value = X;
            X++;
        }
    }