生成随机数字

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