使用基于Fisher-Yates Shuffle的扩展方法Shuffle任意(I)List:

private static Random rng = new Random();  

public static void Shuffle<T>(this IList<T> list)  
{  
    int n = list.Count;  
    while (n > 1) {  
        n--;  
        int k = rng.Next(n + 1);  
        T value = list[k];  
        list[k] = list[n];  
        list[n] = value;  
    }  
}

用法:

List<Product> products = GetProducts();
products.Shuffle();

上面的代码使用了备受批评的系统。选择交换候选的随机方法。它速度很快，但并不像它应该的那样随机。如果你需要更好的随机质量，可以使用System.Security.Cryptography中的随机数生成器，如下所示:

using System.Security.Cryptography;
...
public static void Shuffle<T>(this IList<T> list)
{
    RNGCryptoServiceProvider provider = new RNGCryptoServiceProvider();
    int n = list.Count;
    while (n > 1)
    {
        byte[] box = new byte[1];
        do provider.GetBytes(box);
        while (!(box[0] < n * (Byte.MaxValue / n)));
        int k = (box[0] % n);
        n--;
        T value = list[k];
        list[k] = list[n];
        list[n] = value;
    }
}

一个简单的比较可以在这个博客(WayBack Machine)上找到。

Edit: Since writing this answer a couple years back, many people have commented or written to me, to point out the big silly flaw in my comparison. They are of course right. There's nothing wrong with System.Random if it's used in the way it was intended. In my first example above, I instantiate the rng variable inside of the Shuffle method, which is asking for trouble if the method is going to be called repeatedly. Below is a fixed, full example based on a really useful comment received today from @weston here on SO.

Program.cs:

using System;
using System.Collections.Generic;
using System.Threading;

namespace SimpleLottery
{
  class Program
  {
    private static void Main(string[] args)
    {
      var numbers = new List<int>(Enumerable.Range(1, 75));
      numbers.Shuffle();
      Console.WriteLine("The winning numbers are: {0}", string.Join(",  ", numbers.GetRange(0, 5)));
    }
  }

  public static class ThreadSafeRandom
  {
      [ThreadStatic] private static Random Local;

      public static Random ThisThreadsRandom
      {
          get { return Local ?? (Local = new Random(unchecked(Environment.TickCount * 31 + Thread.CurrentThread.ManagedThreadId))); }
      }
  }

  static class MyExtensions
  {
    public static void Shuffle<T>(this IList<T> list)
    {
      int n = list.Count;
      while (n > 1)
      {
        n--;
        int k = ThreadSafeRandom.ThisThreadsRandom.Next(n + 1);
        T value = list[k];
        list[k] = list[n];
        list[n] = value;
      }
    }
  }
}

这是我最喜欢的shuffle方法，当不需要修改原始的时候。它是Fisher-Yates“由内到外”算法的变体，适用于任何可枚举序列(源的长度不需要从一开始就知道)。

public static IList<T> NextList<T>(this Random r, IEnumerable<T> source)
{
  var list = new List<T>();
  foreach (var item in source)
  {
    var i = r.Next(list.Count + 1);
    if (i == list.Count)
    {
      list.Add(item);
    }
    else
    {
      var temp = list[i];
      list[i] = item;
      list.Add(temp);
    }
  }
  return list;
}

该算法还可以通过分配一个从0到length - 1的范围来实现，并通过将随机选择的索引与最后一个索引交换来随机耗尽索引，直到所有索引都被选中一次。上面的代码完成了完全相同的事情，但没有额外的分配。非常简洁。

With regards to the Random class it's a general purpose number generator (and If I was running a lottery I'd consider using something different). It also relies on a time based seed value by default. A small alleviation of the problem is to seed the Random class with the RNGCryptoServiceProvider or you could use the RNGCryptoServiceProvider in a method similar to this (see below) to generate uniformly chosen random double floating point values but running a lottery pretty much requires understanding randomness and the nature of the randomness source.

var bytes = new byte[8];
_secureRng.GetBytes(bytes);
var v = BitConverter.ToUInt64(bytes, 0);
return (double)v / ((double)ulong.MaxValue + 1);

生成随机双精度(仅在0和1之间)的目的是用于扩展到整数解。如果你需要从一个基于随机双x的列表中选择一个东西，它总是0 <= x && x < 1是很简单的。

return list[(int)(x * list.Count)];

享受吧!

如果我们只需要以完全随机的顺序洗牌项目(只是在一个列表中混合项目)，我更喜欢这个简单而有效的代码，按guid排序项目…

var shuffledcards = cards.OrderBy(a => Guid.NewGuid()).ToList();

正如人们在评论中指出的那样，guid不能保证是随机的，所以我们应该使用真正的随机数生成器:

private static Random rng = new Random();
...
var shuffledcards = cards.OrderBy(a => rng.Next()).ToList();

通过使用元组进行交换，可以使Fisher-Yates shuffle更加简洁和富有表现力。

private static readonly Random random = new Random();

public static void Shuffle<T>(this IList<T> list)
{
    int n = list.Count;
    while (n > 1)
    {
        n--;
        int k = random.Next(n + 1);
        (list[k], list[n]) = (list[n], list[k]);
    }
}

你的问题是如何随机化一个列表。这意味着:

所有独特的组合都应该是可能发生的 所有唯一的组合应该出现在相同的分布(也就是无偏倚)。

由于“随机”，这个问题的大量答案不满足上述两个要求。

下面是一个紧凑的、无偏倚的伪随机函数，遵循Fisher-Yates shuffle方法。

public static void Shuffle<T>(this IList<T> list, Random rnd)
{
    for (var i = list.Count-1; i > 0; i--)
    {
        var randomIndex = rnd.Next(i + 1); //maxValue (i + 1) is EXCLUSIVE
        list.Swap(i, randomIndex); 
    }
}

public static void Swap<T>(this IList<T> list, int indexA, int indexB)
{
   var temp = list[indexA];
   list[indexA] = list[indexB];
   list[indexB] = temp;
}

可以使用morelinq包中的Shuffle扩展方法，它适用于IEnumerables

安装包morelinq

using MoreLinq;
...    
var randomized = list.Shuffle();