从字符串中提取数字，有两种方法：
（1）code:
String str ="abc.htm?id=16034$a=343";
String count=null;
foreach (char c in str)
{
if (c >= '0' && c <= '9')
{
count += c.ToString();
}
else
{
if (count != null)
{
Response.Write(count+"<br/>");
count = null;
}
}
}
if (count != null)
{
Response.Write(count);
count = null;
}
(2) regex:
String str = "abc.htm?id=16034$a=343";
Regex regex = new Regex(@"\d+");
MatchCollection cc= regex.Matches(str, 0);
foreach (Match match in cc)
{
Response.Write(match.Value+"<br/>");
}