FileHandler.cs

public class FileHandler {

    public void SaveTransactionToFile(Transaction transaction) {

        string serializedTransaction = transaction.GetId().ToString();
        serializedTransaction += "," + transaction.Amount.ToString();
        serializedTransaction += "," + transaction.Date.ToString();

        File.WriteAllText("transactions\\" + transaction.GetId() + ".txt", serializedTransaction);
    }

    public void SaveBalanceToFile(double balance) {

        string serializedBalance = balance.ToString();
        File.WriteAllText("balance.txt", serializedBalance);
    }

    public double GetBalanceFromFile() {

        string filePath = "balance.txt";

        if (!File.Exists(filePath)) {

            Console.WriteLine("Could not find file");
            return 0;
        }

        string fileContent = File.ReadAllText(filePath);
        double balance = double.Parse(fileContent);

        return balance;    
    }

    public void DeleteFile(Guid transactionId) {
        File.Delete("transactions\\" + transactionId + ".txt");
    }

    public List<Transaction> GetTransactionsFromFile() {

        List<Transaction> transactions = new List<Transaction>();
        string directoryPath = "transactions\\";

        if (!Directory.Exists(directoryPath)) {

            Console.WriteLine("Transaction not found");
            return transactions;
        }
        
        string[] files = Directory.GetFiles(directoryPath);

        foreach (string file in files)
        {
            string fileContent = File.ReadAllText(file);
        
            string[] parts = fileContent.Split(',');

            if (parts.Length == 3) {

                Transaction transaction = RecreateTransaction(parts);
                transactions.Add(transaction);
            }
        }

        return transactions;
    }

    public Transaction RecreateTransaction(string[] parts) {

        Guid id = Guid.Parse(parts[0]);
        double amount = double.Parse(parts[1]);
        DateTime date = DateTime.Parse(parts[2]);

        return new Transaction(id, date, amount);
    }
}