Is using Random and OrderBy a good shuffle algorithm?

Question

I have read an article about various shuffle algorithms over at Coding Horror. I have seen that somewhere people have done this to shuffle a list:

var r = ne         


        

Answer 1

I found Jon Skeet's answer to be entirely satisfactory, but my client's robo-scanner will report any instance of Random as a security flaw. So I swapped it out for System.Security.Cryptography.RNGCryptoServiceProvider. As a bonus, it fixes that thread-safety issue that was mentioned. On the other hand, RNGCryptoServiceProvider has been measured as 300x slower than using Random.

Usage:

using (var rng = new RNGCryptoServiceProvider())
{
    var data = new byte[4];
    yourCollection = yourCollection.Shuffle(rng, data);
}

Method:

/// 

/// Shuffles the elements of a sequence randomly.
/// 
/// A sequence of values to shuffle.
/// An instance of a random number generator.
/// A placeholder to generate random bytes into.
/// A sequence whose elements are shuffled randomly.
public static IEnumerable Shuffle(this IEnumerable source, RNGCryptoServiceProvider rng, byte[] data)
{
    var elements = source.ToArray();
    for (int i = elements.Length - 1; i >= 0; i--)
    {
        rng.GetBytes(data);
        var swapIndex = BitConverter.ToUInt32(data, 0) % (i + 1);
        yield return elements[swapIndex];
        elements[swapIndex] = elements[i];
    }
}