123456-01,adzxca02,154321-03,aaaaaa-04,123123-05,111111106,456456-07
求助，如何将这个字符串变成01,02,03,04,05,06,07

public string Substring()
{
//加入集合
List<string> list = new List<string>();
list.Add("123456 -01");
list.Add("adzxca02");
list.Add("154321-03");
list.Add("123123-05");
list.Add("111111106");
//循环解析
string strs = "";
foreach (string str in list)
{
strs += str.Substring(-2)+",";
}
strs = strs.Substring(-1);//去掉最后一个，号
return strs;// 返回值：01,02,03,04,05,06
}