asp.net 无重复随机数代码

/// <summary>
        /// 产生无重复随机数
        /// </summary>
        /// <param name="num">个数</param>
        /// <param name="minValue">最小数</param>
        /// <param name="maxValue">最大数</param>
        /// <returns>数组</returns> 
        public int[] getNum(int num, int minValue, int maxValue)
        {
            Random ra = new Random(unchecked((int)DateTime.Now.Ticks));
            int[] arrNum = new int[num];//注意:数组中各元素的初始值是0,当0在取值范围内时要另处理
            int tmp = 0;
            for (int i = 0; i < num; i++)
            {
                tmp = getRandomNum(tmp, minValue, maxValue, ra);//取出值赋到数组中
                if (Array.IndexOf(arrNum, tmp) < 0)//判断是否存在,不存在的话元素tmp的索引应为-1
                {
                    arrNum[i] = tmp;
                }
                else
                {
                    i = i - 1;
                }
            }
            return arrNum;
        }
        public int getRandomNum(int tmp, int minValue, int maxValue, Random ra)
        {
            tmp = ra.Next(minValue, maxValue);
            return tmp;
        }