生成随机数字

 1 方法：
 2 public string RndNum(int VcodeNum)
 3         {
 4             string Vchar = "0,1,2,3,4,5,6,7,8,9";
 5             string[] VcArray = Vchar.Split(new Char[] { ',' });
 6             string VNum = "";
 7             //int temp = -1;
 8             Random rand = new Random();
 9             for (int i = 1; i < VcodeNum + 1; i++)
10             {
11                 int t = rand.Next(10);
12                 VNum += VcArray[t];
13             }
14             return VNum;
15         }
16 调用：string str = RndNum（4）