my solution is this:
DataTable dttmp = ds.Tables[0];
var dic = new Dictionary<String,List<String>>();
for (int i = 0; i < dttmp.Rows.Count; i++)
{
string code = dttmp.Rows[i].ItemArray[0].ToString();
string time = dttmp.Rows[i].ItemArray[1].ToString();
if (code != "0")
{
if (!dic.ContainsKey(code))
dic.Add(code, new List<string>(){time});
else
dic[code].Add(time);
}
}
</string>