用正则吧:^[\u4E00-\u9FA5]+$
string ResultString = null;
string str = "s1.寒34(冰,2";
for (int i = 0; i < str.Length-1; i++)
{
string mystr = str.Substring(i,1);
if (Regex.IsMatch(mystr, "[\u4e00-\u9fa5]"))
ResultString += mystr;
}
Console.Write(ResultString);