Populating data in datagriedview from SQL server if exist add quantity C#

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C#

C#3.5

Iam retrieving data from Sql server to Datagriedview by scanning barcode,i want when data already exist in dataGriedview only to add quantity.I have tried the code below but when i scan the quantity increase but same row is added down,meaning there are two rows of same barcode which is wrong!Please help

What I have tried:

scannedBarcode = textBoxScanBarcode.Text;
            string query = "SELECT Pid,Pname,ScQty As Qty,Price,Discount As Disc_Limit,ActualDiscount, Price As Sub_Total,Percentage,Barcode FROM products,CostAndPrice WHERE products.Pid=CostAndPrice.Fpid AND Barcode='" + scannedBarcode + "'";
            dbObject.readDatathroughAdapter(query, dtScannedProduct);

            //Boolean to check if he has row has been
            bool Found = false;
            if (dataGridViewPurchasedItems.Rows.Count > 0)
            {
               

                //Check if the product Id exists with the same Price
                foreach (DataGridViewRow row in dataGridViewPurchasedItems.Rows)
                {
                    if (Convert.ToString(row.Cells[9].Value) == scannedBarcode)
                    {
                        //Update the Quantity of the found row
                        row.Cells[3].Value = Convert.ToString(1 + Convert.ToInt16(row.Cells[3].Value));
                        Found = true;
                    }

                }
                if (!Found)
                {
                  
                    //Add the row to grid view
                    dataGridViewPurchasedItems.DataSource = dtScannedProduct;
                }

            }
            else
            {
              
                //Add the row to grid view for the first time
                dataGridViewPurchasedItems.DataSource = dtScannedProduct;
            }