数组比较

 protected string newid;//新选择的游戏类别id
        protected string oldnewid;//旧的游戏类别id
        protected string t_id;
      
        protected void Page_Load(object sender, EventArgs e)
        {
            string newid = "2,3,5,6";
            t_id = newid;
            string oldnewid = "1,2,4,6,7";

            string[] arrynewstr = newid.Split(',');

            string[] arryoldnewstr = oldnewid.Split(',');

            ArrayList arr = new ArrayList();

            for (int i = 0; i < arrynewstr.Length; i++)
            {
                for (int j = 0; j < arryoldnewstr.Length; j++)
                {
                    if (arrynewstr[i].Equals(arryoldnewstr[j]))
                        arr.Add(arrynewstr[i].ToString());

                }

            }

            foreach (string filterstr in arr)
            {
                if (newid.IndexOf(filterstr) == 0)
                    newid = newid.Replace(filterstr + ",", "");
                else
                    newid = newid.Replace("," + filterstr, "");

                if (oldnewid.IndexOf(filterstr) == 0)
                    oldnewid = oldnewid.Replace(filterstr + ",", "");
                else
                    oldnewid = oldnewid.Replace("," + filterstr, "");
            }
            Response.Write("最新选择的项目是：" +t_id);
            Response.Write("此为需要对游戏类别表进行相加操作的数据:"+newid);
            Response.Write("<br />");
            Response.Write("此为需要对游戏类别表进行相减的数据:"+oldnewid);