I am a junior developer and my first task at work is to correct a part of a Web Forms project.
The project maps data from an sql server to some variables inside the project and checks if the fields inside the table is null.If everything is ok then it generates an xml file with all the data mapped.
If the variable(CustomerBalance) is null then one error message is generated.
The fact is that even if two or more Customers has null CustomerBalance,only the first one will show up in the UI.

This is the code inside the if statement

foreach (var CustAccnt in CustomerAccounts)
            {
                List<string> accountControllingPersons = new List<string>();

                cmd.CommandText = "SELECT " + datamapping.Where(s => s.CRSElements == "AccOwnerCust").Select(s => s.ColumsNames).FirstOrDefault().ToString() + " FROM " + datamapping.Where(s => s.CRSElements == "AccOwnerCust").Select(s => s.TableNames).FirstOrDefault().ToString() + " where " + datamapping.Where(s => s.CRSElements == "AccOwnerAccount").Select(s => s.ColumsNames).FirstOrDefault().ToString() + " = '" + CustAccnt.Account + "'" + " and " + datamapping.Where(s => s.CRSElements == "AccOwnerRelation").Select(s => s.ColumsNames).FirstOrDefault().ToString() + " !='" + datamapping.Where(s => s.CRSElements == "AccOwnerRelation").Select(s => s.Values).FirstOrDefault().ToString() + "' ";
                cmd.CommandType = CommandType.Text;
                cmd.Connection = sqlConnection1;
                sqlConnection1.Open();
                reader = cmd.ExecuteReader();

                while (reader.Read())
                {
                    accountControllingPersons.Add(reader[datamapping.Where(s => s.CRSElements == "AccOwnerCust").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString());
                }
                sqlConnection1.Close();

                cmd.CommandText = "SELECT " + datamapping.Where(s => s.CRSElements == "CustomerOtherRelationPartyID").Select(s => s.ColumsNames).FirstOrDefault().ToString() + " FROM " + datamapping.Where(s => s.CRSElements == "CustomerOtherRelationPartyID").Select(s => s.TableNames).FirstOrDefault().ToString() + " where " + datamapping.Where(s => s.CRSElements == "CustomerOtherRelationRelatedParty").Select(s => s.ColumsNames).FirstOrDefault().ToString() + " = '" + id + "'";
                cmd.CommandType = CommandType.Text;
                cmd.Connection = sqlConnection1;
                sqlConnection1.Open();
                reader = cmd.ExecuteReader();
                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        accountControllingPersons.Add(reader[datamapping.Where(s => s.CRSElements == "CustomerOtherRelationPartyID").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString());
                    }
                }

                sqlConnection1.Close();
                List<String> TINCountries = new List<String>();
                foreach (var item in accountControllingPersons)
                {
                    cmd.CommandText = "Select distinct " + datamapping.Where(s => s.CRSElements == "TINIssueCountry").Select(s => s.ColumsNames).FirstOrDefault().ToString() +
                                    " from " + datamapping.Where(s => s.CRSElements == "TINCustID").Select(s => s.TableNames).FirstOrDefault().ToString() +
                                    " where " + datamapping.Where(s => s.CRSElements == "TINCustID").Select(s => s.ColumsNames).FirstOrDefault().ToString() +
                                    " = '" + item +
                                    "'  and " + datamapping.Where(s => s.CRSElements == "TINIssueCountry").Select(s => s.ColumsNames).FirstOrDefault().ToString() +
                                    " in (" + inCoutries + ")" +
                                    " and " + datamapping.Where(s => s.CRSElements == "TINIDType").Select(s => s.ColumsNames).FirstOrDefault().ToString() +
                                    " like '" + defaultValues.Where(s => s.Names == "PartyID").Select(s => s.Values).FirstOrDefault().ToString() + "%' "; ;

                    cmd.CommandType = CommandType.Text;
                    cmd.Connection = sqlConnection1;
                    sqlConnection1.Open();
                    reader = cmd.ExecuteReader();
                    while (reader.Read())
                    {
                        TINCountries.Add(reader[datamapping.Where(s => s.CRSElements == "TINIssueCountry").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString());
                    }
                    sqlConnection1.Close();
                }

                foreach (var countr in TINCountries.Distinct())
                {
                    CorrectableAccountReport_Type AccToReport = new CorrectableAccountReport_Type();

                    string Account = CustAccnt.Account;
                    Account AcountData = new Account();
                    string repPeriod = CRScontext.tblBankParams.Where(r => r.Parameter == "ReportingPeriod").Select(r => r.Value).FirstOrDefault();
                    string year = DateTime.Parse(repPeriod).Year.ToString();
                    var custBalances = CRScontext.tblBalances.Where(b => b.CustomerID == id && b.BalanceYear == year && b.CustomerAccount == Account).FirstOrDefault();

                    cmd.CommandText = "SELECT " + customerAccountDataSelect + " FROM " + datamapping.Where(s => s.CRSElements == "AccountID").Select(s => s.TableNames).FirstOrDefault().ToString() + " where " + datamapping.Where(s => s.CRSElements == "AccountID").Select(s => s.ColumsNames).FirstOrDefault().ToString() + " = '" + Account + "'";
                    cmd.CommandType = CommandType.Text;
                    cmd.Connection = sqlConnection1;
                    sqlConnection1.Open();
                    reader = cmd.ExecuteReader();
                    if (custBalances != null)
                    {
                        while (reader.Read())
                        {
                            decimal amount = 0;

                            if (!String.IsNullOrEmpty(custBalances.December))
                            {
                                amount = Convert.ToDecimal(custBalances.December.ToString(), new CultureInfo("en-US"));
                            }
                            string closeDate = reader[datamapping.Where(s => s.CRSElements == "AccCloseDate").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString();
                            DateTime? dateSample;
                            dateSample = null;

                            AcountData = new Account { Closed = Convert.ToBoolean(reader[datamapping.Where(s => s.CRSElements == "AccountClosed").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString()),
                                BalanceAmt = amount,
                                User1 = reader[datamapping.Where(s => s.CRSElements == "AccountcurrCodetype").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString(),
                                User3 = reader[datamapping.Where(s => s.CRSElements == "AccountNumbType").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString(),
                                CloseDate = !string.IsNullOrEmpty(closeDate) ? DateTime.Parse(closeDate) : dateSample,
                                AcStatus= reader[datamapping.Where(s => s.CRSElements == "AcStatus").Select(s => s.ColumsNames).FirstOrDefault().ToString()].ToString()

                            };
                        }
                    }
                    else
                    {
                        HttpContext.Current.Session["Generated"] = "Error! No Balance Record for Account : " + Account;
                        ExceptionUtility.Logger(HttpContext.Current.Session["Generated"].ToString());
                        return null;
                    }

                    sqlConnection1.Close();