函数是这样用,比如100至999的随机数 
Random ran=new Random(); 
int RandKey=ran.Next(100,999); 
不过这样会有重复,可以给Random一个系统时间做为参数，以此产生随机数，就不会重复了 
System.Random a=new Random(System.DateTime.Now.Millisecond); 
int RandKey =a.Next(10);

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Random ran=new Random(seed); 
int num=ran.Next(a,b); 
seed-种子 
a-随机数最小值，b－随机数最大值

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public void RndNum2(int VcodeNum)
     {
         //采用一个简单的算法以保证生成随机数的不同
         SetRow();
         Random rand = new Random();
         for (int i = 1; i < VcodeNum + 1; i++)
         {
             rand = new Random(i * unchecked((int)DateTime.Now.Ticks));
             int t = rand.Next(rows-i+1);
             rec[i - 1] = rowlist[t];
             Move(t,i);
         }
     }
     public void Move(int t,int flag)
     {
         for (int i = t; i < rows - flag; i++)
             rowlist[i] = rowlist[i + 1];
       public void SetRow()
     {
         DataSet mySet = new JY.BLL.love_member().GetWList("grade=3");
         for (int i = 0; i < rows; i++)
             rowlist[i] = mySet.Tables[0].Rows[i]["id"].ToString();