I got this from the C# Programmer's Cookbook. (Great Book.)
using System;
using System.Security.Cryptography;
public class SecureRandomNumberExample {
public static void Main() {
// Create a byte array to hold the random data.
byte[] number = new byte[32];
// Instantiate the default random number generator.
RandomNumberGenerator rng = RandomNumberGenerator.Create();
// Generate 32 bytes of random data.
rng.GetBytes(number);
// Display the random number.
Console.WriteLine(BitConverter.ToString(number));
// Wait to continue.
Console.ReadLine();
}