C# Currency Persistence Class Implementation

Namespace Pers

{
    public class Persistencia
    {
        

Method: Add Currency (AniadirDivisa)

Adds a currency and its value to Divisas.txt if it does not already exist.

public static void AniadirDivisa(String d, double valor)
{
    if (!ExisteDivisa(d))
    {
        StreamWriter sw = new StreamWriter(@"Divisas.txt", true);
        sw.WriteLine(d + "\t" + valor);
        sw.Close();
    }
}

Method: Get Currency Value (ValorDivisa)

Retrieves the value associated with a specific currency symbol.

public static double ValorDivisa(String d)
{
    String v = "";
    StreamReader sr = new StreamReader(@"Divisas.txt");
    String l = sr.ReadLine();
    while (l != null)
    {
        if (l.Contains(d))
        {
            // Extracts the value after the tab separator
            v = l.Substring(l.IndexOf("\t") + 1);
        }
        l = sr.ReadLine();
    }
    sr.Close();
    return Convert.ToDouble(v);
}

Method: Delete Currency (eliminar)

Removes a specified currency entry by copying all other lines to a temporary file, deleting the original, and renaming the temporary file.

public static void Eliminar(String d)
{
    StreamReader sr = new StreamReader(@"Divisas.txt");
    // Note: Appending (true) is used here, but logic implies overwriting content if not careful.
    StreamWriter sw = new StreamWriter(@"Divisas2.txt", false); 
    String l = sr.ReadLine();
    while (l != null)
    {
        if (!l.Contains(d))
        {
            // Correction: Should write the entire line 'l', not just 'd'
            sw.WriteLine(l);
        }
        l = sr.ReadLine();
    }
    sw.Close();
    sr.Close();
    System.IO.File.Delete(@"Divisas.txt");
    File.Move(@"Divisas2.txt", @"Divisas.txt"); // Using Move is cleaner than Copy + Delete
}

Method: Check Existence (ExisteDivisa)

Checks if a currency symbol exists in the file.

public static Boolean ExisteDivisa(String d)
{
    Boolean existe = false;
    StreamReader sr = new StreamReader(@"Divisas.txt");
    String l = sr.ReadLine();
    while (l != null)
    {
        if (l.Contains(d))
        {
            existe = true;
        }
        l = sr.ReadLine();
    }
    sr.Close();
    return existe;
}

Method: List All Currencies (ListarDivisas)

Returns a list of all currency symbols stored in the file.

public static List<String> ListarDivisas()
{
    List<String> ls = new List<String>();
    StreamReader sr = new StreamReader(@"Divisas.txt");
    String l = sr.ReadLine();
    while (l != null)
    {
        // Extracts the currency symbol before the tab separator
        ls.Add(l.Substring(0, l.IndexOf("\t")));
        l = sr.ReadLine();
    }
    sr.Close();
    return ls;
}