using System;
using System.Threading;
 
namespace Recetas.Multithreading.Cap04.R0109
{
    // Representa una cuanta Bancaria:
    public class Cuenta
    {
        // Instancia Object para el bloque concurrente 
        // a un sección crítica:
        private Object bloqueo = new Object();
        private int saldo;
 
        // Objeto Random para simular la cantidad de dinero 
        // a retirar:
        Random aleatorio = new Random();
 
        public Cuenta(int saldoInicial)
        {
            saldo = saldoInicial;
        }
 
        // Retiro de dinero:
        public int Retirar(int cantidad)
        {
            // Comprueba que la cuenta tenga fondos para el retiro:
            if (saldo < 0)
            {
                throw new Exception ("Saldo Negativo.");
            }
 
            // Sección crítica. Sólo se permite una transacción 
            // de retiro de forma simultánea:
            lock (bloqueo)
            {
                if (saldo >= cantidad)
                {
                    Console.WriteLine ("Saldo antes del retiro: {0}", saldo.ToString());
                    Console.WriteLine ("Cantidad a retirar: -{0}", cantidad.ToString());
                    saldo -= cantidad;
                    Console.WriteLine ("Saldo después del retiro: {0}", saldo.ToString());
                    return cantidad;
                }
                else
                {
                    return 0;
                }
            }
        }
 
        // Simula la ejecución de 100 transacciones:
        public void RealizarTransaccion()
        {
            for (int i = 1; i <= 100; ++i)
            {
                // Realiza retiros entre 1 y 100 unidades monetarias:
                Retirar(aleatorio.Next(1, 101));
            }
        }
    }
 
    public sealed class Banco
    {
        public static void Main()
        {
            Console.Title = "Uso de lock para transacciones bancarias";
            Console.WriteLine ();
 
            // Crea un arreglo de 10 threads:
            Thread[] threads = new Thread[10];
 
            // Una cuenta para arealizar transacciones, 
            // y un saldo inicial de 1000 unidades monetarias:
            Cuenta c = new Cuenta(1000);
 
            // Crea las 10 instancias de Thread:
            for (int i = 0; i < 10; ++i)
            {
                Thread t = new Thread(new ThreadStart(c.RealizarTransaccion));
                threads[i] = t;
            }
 
            // Inicia los threads para ejecución simultánea:
            for (int i = 0; i < 10; ++i)
            {
                threads[i].Start();
            }
 
            Console.WriteLine ();
        }
    }
}

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