How to update or modifying customized template fields from existing quickbooks invoice using QBFC

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C#

Quickbooks

I need to update two custom field in some invoices (I created this field in customer custom fields first uuid second filed uuid2 ) and i have not been able to figure out how to update it using c#. how can i update QuickBooks Desktop Custom Fields Data using the QBFC SDK i tried this
//create class invoice

 public class Invoice
{
    public string InvoiceNumber { get; set; }
    public string Item { get; set; }
    public string TxnDate { get; set; }
    public double Quantity { get; set; }
    public string ItemCode { get; set; }
    public string ItemDescription { get; set; }
    public string Note { get; set; }
    public string UpcCode { get; set; }
    public string UnitPrice { get; set; }
    public string TotalPrice { get; set; }
    public string PerUnit { get; set; }
    //
    public string CustomerName { get; set; }
    public string BillAddressAdd1 { get; set; }
    public string BillAddressAdd2 { get; set; }
    public string BillAddressCity { get; set; }
    public string BillAddressState { get; set; }
    public string BillAddressPostalCode { get; set; }
    public string Phone { get; set; }
    public string Fax { get; set; }
    public string Memo { get; set; }
    public string ListId { get; set; }
    public string EditSequence { get; set; }
    public string OwnerID { get; set; }
    public string uuid { get; set; }
    public string uuid2 { get; set; }
    

}
//create function UpdateINVOICE
<pre>enter code here public bool UpdateINVOICE(Invoice invoice)
    {
        try
        {
            sessionManager = new QBSessionManager();

            IMsgSetRequest requestMsgSet = sessionManager.CreateMsgSetRequest(countryQB, majorVersionQB, minorVersionQB);
          
            requestMsgSet.Attributes.OnError = ENRqOnError.roeContinue;
            IInvoiceMod invoiceModRq = requestMsgSet.AppendInvoiceModRq();
            IDataExtAdd DataExtAddRq = requestMsgSet.AppendDataExtAddRq();
         DataExtAddRq.OwnerID.SetValue("0"); 
                               
                            if (invoice.Memo != null)
                invoiceModRq.Memo.SetValue(invoice.Memo);
            if (invoice.ListId != null)
                invoiceModRq.TxnID.SetValue(invoice.ListId);
            if (invoice.EditSequence != null)
                invoiceModRq.EditSequence.SetValue(invoice.EditSequence);
            DataExtAddRq.ORListTxnWithMacro.ListDataExt.ListDataExtType.SetValue(ENListDataExtType.ldetCustomer);
            DataExtAddRq.ORListTxnWithMacro.ListDataExt.ListObjRef.FullName.SetValue("cust1");
          
            DataExtAddRq.DataExtName.SetValue("uuid"); 
         DataExtAddRq.DataExtValue.SetValue(invoice.uuid);
               DataExtAddRq.DataExtName.SetValue("uuid2"); 
            DataExtAddRq.DataExtValue.SetValue(invoice.uuid2);
            OpenConnection();
            IMsgSetResponse responseMsgSet = sessionManager.DoRequests(requestMsgSet);
            
            CloseConnection();
           IResponse response = responseMsgSet.ResponseList.GetAt(0);
           

            if (response.StatusCode != 0)
            {
                throw new Exception($" Error: {response.StatusMessage}");
               
            }

            return true;

        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            CloseConnection();
        }
    }

Custom fields can't update
The problem is that the previous code does not work. He cannot update the uuid and uuid2 fields, although he can update the memo field. I think the reason is that I am trying to update the custom fields data for customers. Is there a better way than the previous code or what is the error in my code?

What I have tried:

The problem is that the previous code does not work. He cannot update the uuid and uuid2 fields, although he can update the memo field. I think the reason is that I am trying to update the custom fields data for customers. Is there a better way than the previous code or what is the error in my code?