前面有人提了方法，大老鹰也提了意见

我这里给出一个更简单的办法，请批评指正

string input = "DONGFANGZHIZHU19770822";

string alpha = "";
string number = "";

foreach(char c in input) {
     if (Char.IsNumber(c))
         number += c;
     else
         alpha += c;
}