public void AddNewDebtor(Debtor debtor, Debt debt)
        {
            SqlConnection sqlcon = new SqlConnection(connectionString);

            string debtorInsert = "INSERT INTO Debtors" + "(DebtorId, Name, TotalDebt)" + "VALUES" +
                                  $"({debtor.Id}, '{debtor.Name}', {debtor.TotalDebt})";
            string debtInsert = "INSERT INTO Debts" +
                                "(DebtorId, Date, DebtValue)" +
                                "VALUES" +
                                $"({debtor.Id}, '{debt.Date}', {debtor.TotalDebt})";

            try
            {
                sqlcon.Open();

                SqlCommand debtorInsertCommand = new SqlCommand(debtorInsert, sqlcon);
                SqlCommand debtInsertCommand   = new SqlCommand(debtInsert, sqlcon);

                debtorInsertCommand.ExecuteNonQuery();
                debtInsertCommand.ExecuteNonQuery();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                sqlcon.Close();
            }
        }
        public ICollection <Debt> GetDebtsFor(int ID)
        {
            SqlConnection sqlcon = new SqlConnection(connectionString);
            ObservableCollection <Debt> debts = new ObservableCollection <Debt>();

            SqlCommand cmd = new SqlCommand("SELECT * FROM Debts WHERE DebtorID=" + ID, sqlcon);

            try
            {
                sqlcon.Open();
                SqlDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    Debt debt = new Debt((int)reader["DebtValue"], (DateTime)reader["Date"]);
                    debts.Add(debt);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                sqlcon.Close();
            }

            return(debts);
        }