Parallel.Foreach giving error " Index was outside the bounds of the array "

Question

I am facing some problem in parallel.foreach which is "Index was outside the bounds of the array". I am attaching some code for parallel.foreach and where it is crashing.

 var lstFRItems = session.CreateCriteria<TFRItem>().Add(Restrictions.Eq("TSCEnterprise.FEnterpriseID", EnterpriseId)).AddOrder(Order.Asc("FName")).List<TFRItem>();
                    List<FRItemAccount> lstItemAccount = new List<FRItemAccount>();
                    var ListAccounts = session.CreateCriteria<TFRItemAccount>().List<TFRItemAccount>();   //lstFRItems.Select(i => new  { i.TFRItemAccounts }).ToList();
                    //foreach (var item in lstFRItems)
                Parallel.ForEach(lstFRItems, item =>
                 {
                     var lstItemAcc = ListAccounts.Where(i => i.TFRItem == item); //item.TFRItemAccounts.ToList();
                     FRItemAccount account = new FRItemAccount();
                     account.ItemID = item.FItemID;
                     account.ItemAccount = new List<ItemAccount>();
                   //  foreach (var itemAcct in lstItemAcc)
                    Parallel.ForEach(lstItemAcc, itemAcct =>
                     {
                         ItemAccount oItemAccount = new ItemAccount();
                         if (itemAcct != null)
                         {
                             oItemAccount.ItemAccountID = itemAcct.FItemAccountID;

                             if (itemAcct.TSCProperty == null)
                             {
                                 oItemAccount.ForID = itemAcct.TSCCompany.FCompanyID;
                                 oItemAccount.ForCompanyName = "Co#  " + "- " + itemAcct.TSCCompany.FID + " " + itemAcct.TSCCompany.FName;
                                 oItemAccount.FID = itemAcct.TSCCompany.FID;
                                 oItemAccount.ForType = 1;
                             }
                             else
                             {
                                 oItemAccount.ForID = itemAcct.TSCProperty.FPropertyID;
                                 oItemAccount.ForCompanyName = "Prop#  " + "- " + itemAcct.TSCProperty.FID + " " + itemAcct.TSCProperty.FName;
                                 oItemAccount.FID = itemAcct.TSCProperty.FID;
                                 oItemAccount.ForType = 2;
                             }
                             oItemAccount.Account = itemAcct.FAccount;
                             account.GLAccount = itemAcct.FAccount.ToString("#0.000"); //Formatted by Lhore Bansal
                            // account.Account = itemAcct.FAccount;
                             oItemAccount.isExisting = true;
                             //Original TFRItemAccount
                             oItemAccount.orgItemAccount = itemAcct;
                         }
                         if (lstItemAcc == null)
                             account.ItemID = item.FItemID;
                         account.ItemAccount.Add(oItemAccount);
                     });
                     //Original tFRItem
                     account.Item = item;
                     //account.BaseAccount = Convert.ToDouble(item.FBaseAccount.ToString("F0")); // commented by jeet
                     account.BaseAccount = Convert.ToDouble((int)item.FBaseAccount); // added by jeet
                     account.Name = item.FName;
                     account.Type = item.FType;
                     lstItemAccount.Add(account);
                 });
                  //  tx.Commit();
                    return Item = lstItemAccount;

It is crashing at third last line "lstItemAccount.Add(account)". When I saw in lstItemAccount, It has some counts and in base section it has a error "base {System.SystemException} = {"Source array was not long enough. Check srcIndex and length, and the array's lower bounds."}".

What is the solution of this error?

Answer 1

I would use a ConcurrentBag<T> instead of List<T>. List<T> is designed for only one thread's access.