Randomization

//Related to Question at:
//http://groups.google.com/group/dotnetdevelopment/browse_thread/thread/7e6a6815d8d855f9

using System;
using System.Threading;

interface IFoo
{
  void foo(int a, int b);
}

class Factory : IFoo
{
  private enum Operation
  {
    add = 1,
    subtract = 2,
    multiply = 3,
    divide = 4,
  }

  private int _a, _b;
  private int randomSeed = 0;

  public virtual void foo(int a, int b)
  {

    this._a = a;
    this._b = b;

    Random rand = new Random(randomSeed);

    Operation op = (Operation)rand.Next(1, 5);

    switch (op)
    {
      case Operation.add:
        plus();
        break;
      case Operation.subtract:
        minus();
        break;
      case Operation.multiply:
        multiplier();
        break;
      case Operation.divide:
        dividor();
        break;
    }

    //if (rand.Next(4) % 4 == 0)
    //  plus();
    //else if (rand.Next() % 4 == 1)
    //  minus();
    //else if (rand.Next() % 4 == 2)
    //  dividor();
    //else multiplier();
  }

  public void plus()
  {
    Console.WriteLine("{0}+{1}={2}", _a, _b, _a + _b);
  }

  public void minus()
  {
    Console.WriteLine("{0}-{1}={2}", _a, _b, _a - _b);
  }

  public void dividor()
  {
    Console.WriteLine("{0}/{1}={2}", _a, _b, _a / _b);
  }

  public void multiplier()
  {
    Console.WriteLine("{0}*{1}={2}", _a, _b, _a * _b);
  }

  public int RandomSeed
  {
    set { randomSeed = value; }
  }

}
class MainClass
{
  static void Main(string[] args)
  {
    IFoo[] df = new IFoo[10];
    for (int i = 0; i < 10; i++)
    {
      Factory f = new Factory();

      // Uncomment only one of the below 3 approaches at a time:
      //SleepingWithRandom(ref f, i);
      LoopingRandom(ref f, i);
      //ComplementingRandom(ref f, i);

      df[i] = f;
    }
  }

  private static void SleepingWithRandom(ref Factory f, int i)
  {
    // Generate a seed from the current time and set the seed value of the Random to be created.
    f.RandomSeed = unchecked((int)(DateTime.Now.Ticks));
    f.foo(i + 1, i + 1);

    // Initiate a delay so as to increase randomness.
    Thread.Sleep(20);
  }

  private static void LoopingRandom(ref Factory f, int i)
  {
    // Generate a different seed using the loop variable itself.
    f.RandomSeed = i;
    f.foo(i + 1, i + 1);
  }

  private static void ComplementingRandom(ref Factory f, int i)
  {
    // Generate a different seed based on whether the loop variable is even or odd.
    if (i % 2 == 0)
      f.RandomSeed = ~unchecked((int)(DateTime.Now.Ticks));
    else
      f.RandomSeed = unchecked((int)(DateTime.Now.Ticks));

    f.foo(i + 1, i + 1);
  }

}