使用C#中Random函数获取随机值的时候出现的问题（100分）

[wfyloo1981]

问题现象：程序如果直接运行得出的结果就是固定顺序的值；如果在其中其中Main中GetRandomCards方法的建立Random对象处加上断点的话，得出的内容就是随机的了。

代码功能：从搅乱的一副牌中取出5张牌，如果5张牌都是相同花色，在屏幕上显示5张牌和"Flush"字样；否则在屏幕上显示5张牌和"No Flush"字样。
代码来源：《C#入门经典》第十章练习4
代码如下：
Main

 class Program
    {
        static void Main(string[] args)
        {
            Deck myDeck = new Deck();
            myDeck.Shuffle();
            Card[] fiveCards = GetRandomCards(myDeck, 5);
            bool diffentSuit = false;
            for (int i = 1; i < fiveCards.Length; i++)
            {
                if (fiveCards[i - 1].suit != fiveCards[i].suit)
                {
                    diffentSuit = true;
                    break;
                }
            }

            for (int i = 0; i < fiveCards.Length; i++)
                Console.WriteLine("No.{0} card is {1}", i + 1, fiveCards[i].ToString());

            if (diffentSuit == true)
                Console.WriteLine("No Flush!");
            else
                Console.WriteLine("Flush!");
            
            Console.ReadKey();
        }

        static Card[] GetRandomCards(Deck myDeck, int count)
        {
            Card[] cards = new Card[count];
            Random random = new Random();
            int[] hasFoundIndexs = new int[count];
            for (int i = 0; i < count; i++)
            {
                int index = -1;
                bool hasFound = false;
                do
                {
                    hasFound = false;
                    index = random.Next(52);
                    for (int j = 0; j < i; j++)
                    {
                        if (hasFoundIndexs[j] == index)
                        {
                            hasFound = true;
                            break;
                        }
                    }
                }
                while (hasFound == true);

                cards[i] = myDeck.GetCard(index);
                hasFoundIndexs[i] = index;
            }
            
            return cards;
        }
    }

Card类：一张扑克牌

   public class Card
    {
        public readonly Rank rank;
        public readonly Suit suit;

        private Card()
        {
        }

        public Card(Suit newSuit, Rank newRank)
        {
            rank = newRank;
            suit = newSuit;
        }

        public override string ToString()
        {
            return "The " + rank + " of " + suit + "s";
        }
    }

Deck类：一副扑克牌

  public class Deck
    {
        private Card[] cards;
    
        public Deck()
        {
            cards = new Card[52];
            for (int suitVal = 0; suitVal < 4; suitVal++)
            {
                for (int rankVal = 1; rankVal < 14; rankVal++)
                {
                    cards[suitVal * 13 + rankVal - 1] = new Card((Suit)suitVal, (Rank)rankVal);
                }
            }

        }

        public Card GetCard(int cardNum)
        {
            if (cardNum >= 0 && cardNum <= 51)
                return cards[cardNum];
            else
                throw (new System.ArgumentOutOfRangeException("cardNum", cardNum, "Values must be between 0 and 51."));
        }

        public void Shuffle()
        {
            Card[] newDeck = new Card[52];
            bool[] assigned = new bool[52];
            Random sourceGen = new Random();
            for (int i = 0; i < 52; i++)
            {
                int deskCard = 0;
                bool foundCard = false;
                while (foundCard == false)
                {
                    deskCard = sourceGen.Next(52);
                    if (assigned[deskCard] == false)
                        foundCard = true;
                }
                assigned[deskCard] = true;
                newDeck[deskCard] = cards[i];
            }
            newDeck.CopyTo(cards, 0);
        }
    }

[liherun]

随即数是根据时间得出来的，程序执行很快的，你的2次执行的时间差很小，所以随机数是一样的
sleep(10)

[liherun]

在

hasFoundIndexs[i] = index;

后
或者

index = random.Next(52);

前
加上

Thread.Sleep(10);

试试

[rqx110]

http://blog.miniasp.com/post/2008/05/Random-vs-RNGCryptoServiceProvider.aspx
建议LZ看下这篇文章，random其实有时候真的不够随机。

[wartim]

        // 摘要:
        //     使用与时间相关的默认种子值，初始化 System.Random 类的新实例。
        public Random();

Thread.Sleep

[wartim]

看错了，按你这段，和种子数没关系，应该是随机的，只要不是连续new而没有sleep：sourceGen = new Random();

[angieduan]

Random sourceGen = new Random(new Guid().GetHashCode());