Dictionary<string, string> List = new Dictionary<string, string>();
            List.Add("01", "aaa");
            List.Add("0105", "aaa");
            List.Add("010501", "aaa");
            string str = "0105";
            Dictionary<string, string> ListB = new Dictionary<string, string>();
            foreach (KeyValuePair<string, string> kvp in List)
            { 
                if(kvp.Key==str)
                    continue;
                if (str.StartsWith(kvp.Key))
                {
                    ListB.Add(kvp.Key, kvp.Value);
                }
            }
            foreach (KeyValuePair<string, string> kvp in List)
            {
                if (kvp.Key == str)
                    continue;
                if (kvp.Key.StartsWith(str))
                {
                    ListB.Add(kvp.Key, kvp.Value);
                }
            }

------解决方案--------------------

上面的bss代码断开了，更正一下：
C# code
class 科目树
{
    Dictionary<string, 科目树> 下级子科目= new Dictionary<string, 科目树>;
    Entity 本级别的数据;
}