Unable to cast object of type 'APDocumentResult' to type 'PX.Data.PXResult`1[PX.Objects.AP.APDocumentEnq+APDocumentResult]'

Getting the above error in vendors details; Upgraded from 2020r2 to 2022r2.

what could be the issue?

kindly assist, all responses will be highly appreciated.

see full code below;

using System;
using System.Collections.Generic;
using System.Collections;
using PX.Data;
using PX.Objects.GL;
using PX.Objects.CS;
using PX.Objects.CM;
using PX.Objects;
using PX.Objects.AP;

namespace PX.Objects.AP
{
    public class APDocumentEnq_Extension : PXGraphExtension<APDocumentEnq>
    {


        public PXSelectOrderBy<APDocumentEnq.APDocumentResult, OrderBy<Asc<APDocumentEnq.APDocumentResult.docDate>>> Documents;
        protected virtual IEnumerable documents()
        {
            decimal decCurrRunningBal = 0;
            decimal decRunningBal = 0;
            Dictionary<string, decimal> curydict = new Dictionary<string, decimal>();

            BqlCommand query = Base.Documents.View.BqlSelect;
            PXView view = new PXView(Base, true, query, Base.Documents.View.BqlDelegate);

            int intStartRow = PXView.StartRow;
            int intTotalRows = 0;



            List<Object> list = view.Select(PXView.Currents, PXView.Parameters, PXView.Searches, PXView.SortColumns, PXView.Descendings, PXView.Filters, ref intStartRow, PXView.MaximumRows, ref intTotalRows);
            PXView.StartRow = 0;

            foreach (PXResult<APDocumentEnq.APDocumentResult> item in list)
            {
                 APDocumentEnq.APDocumentResult row = item;
                APRegisterExt registerExt = this.Base.Documents.Cache.GetExtension<APRegisterExt>(row);

                //KES Running Balance  
                decRunningBal += row.OrigDocAmt ?? 0;
                //ed
                //Foreign Running Balance
                if (row.CuryID != "KWH")
                {
                    if (curydict.ContainsKey(row.CuryID))
                    {
                        curydict[row.CuryID] += row.CuryOrigDocAmt ?? 0;
                        decCurrRunningBal = curydict[row.CuryID];
                    }
                    else
                    {
                        curydict[row.CuryID] = row.CuryOrigDocAmt ?? 0;
                        decCurrRunningBal = curydict[row.CuryID];
                    }

                    //ed decCurrRunningBal += row.CuryOrigDocAmt ?? 0;

                }
                    registerExt.UsrCurrencyRbal = decCurrRunningBal;
                    registerExt.UsrVenderbal = decRunningBal;
            }
            return list;

            }
             //CODE FOR DISPLAYING DOCUMENT TAX
            protected void APDocumentResult_RowSelected(PXCache cache, PXRowSelectedEventArgs e)
            {
              APDocumentEnq.APDocumentResult row = (APDocumentEnq.APDocumentResult)e.Row;
              if(row == null) return;
              APRegisterExt extObj = cache.GetExtension<APRegisterExt>(row);
              APInvoice invoiceObj = PXSelect<APInvoice, Where<APInvoice.refNbr, Equal<Required<APInvoice.refNbr>>,
                And<APInvoice.docType, Equal<Required<APInvoice.docType>>>>>.Select(this.Base, row.RefNbr, row.DocType);

              if(invoiceObj != null)
                {
                  extObj.UsrTaxAmt = invoiceObj.CuryTaxTotal;
                  //cache.SetValue<APRegisterExt.usrTaxAmt>(e.Row,invoiceObj.CuryTaxTotal);
                  if(invoiceObj.CuryTaxTotal> 0) extObj.UsrTwopercent = (invoiceObj.CuryTaxTotal * 0.125m);
                  //var result = invoiceObj.CuryTaxTotal * 0.125m;
                  //if(invoiceObj.CuryTaxTotal> 0) cache.SetValue<APRegisterExt.usrTwopercent> (e.Row,result);
                }
            }
        }
    }