关于生成随机数字的问题?

Question

我写了个生成12位字符串的函数,生成的字符串前四位是字母组成,后8位是数字组成当我在此基础上生成10个不同的字符串的时候.我这样做的,用FOR循环读取10次这个函数但是每次生成的字符串都是一样的,这个问题一直让我头疼,请各位指点迷津~~

Answer 1

 int number;
        char code;
        string checkCode = String.Empty;        System.Random random = new Random();
        for (int j = 0; j < 4; j++)
        {
            number = random.Next();
            if (number % 2 != 0)
            {
                code = (char)('A' + (char)(number % 26));
                checkCode += code.ToString();
            }
            else
            {
                j--;
            }
        }
        for (int i = 0; i < 8; i++)
        {
            number = random.Next();            if (number % 2 == 0)
            {
                code = (char)('0' + (char)(number % 10));
                checkCode += code.ToString();
            }
            else
            {
                i--;
            }
        }        Response.Write(checkCode.ToString());

Answer 2

public static string rc()
    {
        char[] arrchar = new char[]{
            '0','1','2','3','4','5','6','7','8','9',
       'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
       };
        StringBuilder num = new StringBuilder();
        Random rnd = new Random(DateTime.Now.Millisecond);
        for (int i = 1; i <= 4; i++)
        {
            //num2.Append(arrchar[rnd.Next(0,10)].ToString());
            //num.Append(arrchar[rnd.Next(0, 10)].ToString());
            num.Append(arrchar[rnd.Next(11, arrchar.Length)].ToString());
        }
        for (int j = 1; j <= 8; j++)
        {
            num.Append(arrchar[rnd.Next(0,10)].ToString());
        }
            return num.ToString();
    }

Answer 3

http://topic.csdn.net/u/20071225/16/60a0e08a-a096-4fce-a5d8-65346943b89c.html

Answer 4

        private string getString(Random s,Random n)
        {
            string strString = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
            string strNumber = "0,1,2,3,4,5,6,7,8,9";
            string strStr = null;
            string strNum = null;
            string strTemp = null;
            int k;
            string[] strs = strString.Split(',');
            string[] strn = strNumber.Split(',');
            for (int i = 0;; i++)
            {
                k = s.Next(26);
                strTemp = strs[k].ToString();
                if (strTemp == "*")
                    continue;
                strs[k] = "*";
                    strStr += strTemp;
                if (strStr.Length == 4)
                    break;
            }
            for (int i = 0; ; i++)
            {
                k = n.Next(10);
                strTemp = strn[k].ToString();
                if (strTemp == "*")
                    continue;
                else
                    strn[k] = "*";
                    strNum += strTemp;
                if (strNum.Length == 8)
                    break;
            }            return strStr + strNum;
        }        private void getStr()
        {
            Random rand1 = new Random();
            Random rand2 = new Random();
            for(int i=0;i<10;i++)
            {
                Response.Write(getString(rand1,rand2)+"<br />");
            }
        }单个不包含重复，

Answer 5

private string   strString   =   {"a","b","c","d","e","f","g","h","i","j","k","l","m","n",
                          "o","p","q","r","s","t","u","v","w","x","y","z"}; 
private string   strNumber   =   {"0',"1","2","3","4","5","6","7","8","9"}; 
private Random rand = new Random();
private ArrayList arr = new ArrayList(); //存放最后生成的10个字符串private string GetRandString()
{
  string stringStr = string.Empty;
  for(int i = 0; i < 4; i++)
  {
    numStr += strString[rand.Next(26)];
  }
  return numStr;
}private string GetRandNumber()
{
  string numStr = string.Empty;
  for(int i = 0; i < 8; i++)
  {
    numStr += strNumber[rand.Next(10)];
  }
  return numStr;
}private string GetDemandString()
{
  return GetRandString()+GetRandNumber();
}private void GetTenString()   //也可以直接返回一个集合对象
{
  string temp = string.Empty;
  for(int i=0; i<10; i++)
  {
    temp = GetDemandString();
    if(arr.Count < 1)
    {
       arr.Add(temp);
    }
    else
    {
      while(arr.Contains(temp))
      {
        temp = GetDemandString();
      }
      arr.Add(temp);
    }
  }
}

Answer 6

不好意思， GetRandString() 中的numStr 应改为stringStr