数组分组

为什么这样子写 分组不成功，  调试最后的  listItemCount的时候 ，  AllGroup就会改变原来的值

static void Main(string[] args)
        {
            List<string> strList = new List<string>();
            strList.Add("1.png");
            strList.Add("2.png");
            strList.Add("3.png");
            strList.Add("4.png");
            strList.Add("5.png");
            strList.Add("6.png");
            strList.Add("7.png");
            strList.Add("8.png");
            strList.Add("9.png");
            strList.Add("10.png");


            List<List<string>> AllGroup = new List<List<string>>();

            int recordCount = 0;
            int listItemCount = 0;
            List<string> group = new List<string>();
            for (listItemCount = 0; listItemCount < strList.Count; listItemCount++)
            {
                if (recordCount < 3)
                {
                    group.Add(strList[listItemCount]);
                    recordCount++;
                }
                else
                {
                    AllGroup.Add(group);
                    group.Clear();
                    group.Add(strList[listItemCount]);
                    recordCount = 1;
                }
            }

        }