大家帮我看看这个生成随机字符怎么生成的9个都一模一样呢？

Question

        for (int i = 0; i < 10; i++)
        {
            Response.Write(Make(3,8)+"</br>");
        } public static string Make(int kind, int pwdlen)
    {
        string tmpstr = "", pwdchars = "";
        int iRandNum;
        switch ( kind )
        {
            case 1: pwdchars = "1234567890";
                break;
            case 2: pwdchars = "abcdefghijklmnopqrstuvwxyz";
                break;
            case 3: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                break;
            case 4: pwdchars = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";
                break;
            case 5: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
                break;
            case 6: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ~!#$%^&*";
                break;
            default: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                break;
        }
        Random rnd = new Random();
        for (int i = 0; i < pwdlen; i++)
        {
            iRandNum = rnd.Next(pwdchars.Length);
            tmpstr += pwdchars[iRandNum];
        }
        return tmpstr;
    }
 怎么打印出来的都是一样的呢？只有刷新页面才会改变。

Answer 1

这个随机数再每次调用make函数的时候怎么会生成的一模一样呢？

Answer 2

修改如下，即可            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine(Make(3, 8,i));
            }
            Console.ReadKey();        public static string Make(int kind, int pwdlen,int seed)
        {
            string tmpstr = "", pwdchars = "";
            int iRandNum;
            switch (kind)
            {
                case 1: pwdchars = "1234567890";
                    break;
                case 2: pwdchars = "abcdefghijklmnopqrstuvwxyz";
                    break;
                case 3: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                    break;
                case 4: pwdchars = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";
                    break;
                case 5: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
                    break;
                case 6: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ~!#$%^&*";
                    break;
                default: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                    break;
            }
            Random rnd = new Random(seed);
            for (int i = 0; i < pwdlen; i++)
            {
                iRandNum = rnd.Next(pwdchars.Length);
                tmpstr += pwdchars[iRandNum];
            }
            return tmpstr;
        }

Answer 3

像我在3樓的代碼這樣，如果你每次給random類的種子不一樣，就可以確保不會重復。

Answer 4

for (int i = 1; i < 7; i++)
        {
            Response.Write(Make(i,8)+"</br>");
        } public static string Make(int kind, int pwdlen)
    {
        string tmpstr = "", pwdchars = "";
        int iRandNum;
        switch ( kind )
        {
            case 1: pwdchars = "1234567890";
                break;
            case 2: pwdchars = "abcdefghijklmnopqrstuvwxyz";
                break;
            case 3: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                break;
            case 4: pwdchars = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";
                break;
            case 5: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
                break;
            case 6: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ~!#$%^&*";
                break;
            default: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                break;
        }
        Random rnd = new Random(pwdchars.Length);
        for (int i = 0; i < pwdlen; i++)
        {
            iRandNum = rnd.Next(pwdchars.Length);
            tmpstr += pwdchars[iRandNum];
        }
        return tmpstr;
    }

Answer 5

for (int i = 0; i < 10; i++)
{
    Response.Write(Make(3,8)+"</br>");
}Random rnd = new Random(); 是在循环中创建的，不会真正的随机。
应该把rnd放在循环外创建。或者Random rnd = new Random((int)DateTime.Now.Ticks); 

Answer 6

比較保險的方法是，使用Environment.TickCount作為種子數，重復的可能性更小               Random rnd = new Random(Environment.TickCount - seed);

Answer 7

static Random rnd = new Random();        public static string Make(int kind, int pwdlen)
        {
            string tmpstr = "", pwdchars = "";
            int iRandNum;
            switch (kind)
            {
                case 1: pwdchars = "1234567890";
                    break;
                case 2: pwdchars = "abcdefghijklmnopqrstuvwxyz";
                    break;
                case 3: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                    break;
                case 4: pwdchars = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";
                    break;
                case 5: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
                    break;
                case 6: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ~!#$%^&*";
                    break;
                default: pwdchars = "1234567890abcdefghijklmnopqrstuvwxyz";
                    break;
            }            for (int i = 0; i < pwdlen; i++)
            {
                iRandNum = rnd.Next(pwdchars.Length);
                tmpstr += pwdchars[iRandNum];
            }
            return tmpstr;
在外部声明rnd即可 Random的无参构造函数取系统当前时间做为seed, 如果程序足够快, 每次的seed是相同的, 生成的随机也就相同

Answer 8

增加一个与Make方法同级别的静态成员。在Make方法中直接使用。
像8楼那样
那个成员的名称可以起得好认一些。