Datagridviewcomboboxcell Error: datagridviewcomboboxcell value is not valid c#

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C#

C#4.0

DataGridView

Trying to fill the datagridviewcomboboxcell using datagridview.rows.add method. It shows the first value instead of the actual value. But if i Read the value of the current cell then it shows the correct value. if i don't use the event DataError then it shows me exception "datagridviewcomboboxcell value is not valid".

Here is my code

private void AutoCompleteCustomer()
      {
               foreach (DataGridViewRow row in dgvCustomer.Rows)
           {
               DataGridViewComboBoxCell nameCell = ((DataGridViewComboBoxCell)row.Cells["colCustomerName"]);
               nameCell.Items.Clear();
               var custInfo = newDB.CustomerTbls.Where(s => s.Status == "Active" & s.Type == "Customer").Select(s => s);
               foreach (var c in custInfo)
               {
                   nameCell.Items.Add("(" + c.Id + ") " + c.Name);
               }
           }
       }

   private void dgvCustomer_RowsAdded(object sender, DataGridViewRowsAddedEventArgs e)
   {
       AutoCompleteCustomer();
   }

here is the Fill Code which fills the datagridview on form load

private void FillForm()
    {
        lblInvoiceNumber.Text = InvoiceNumber;
        lblItemName.Text = leslieDB.GAItemTbls.Where(i => i.Status == "Active" & i.PartNo == _partNo).Select(i => i.Name).Single();
        var relInfo = from r in leslieDB.GARelationTbls.Where(r => r.Item_PartNo == _partNo & r.InvoiceNumber == InvoiceNumber & r.Status == "Active")
                      join c in leslieDB.CustomerTbls on r.Customer_Id equals c.Id
                      where c.Status == "Active" & c.Type == "Customer"
                      select new
                     {
                         r.Id,
                         Name = c.Name,
                         cId = c.Id,
                         r.Quantity
                     };
        foreach (var re in relInfo)
        {
            dgvCustomer.Rows.Add(re.Id, "(" + re.cId + ") " + re.Name, re.Quantity);
        }
    }