//提取字符串中至少连续7位的数字
string txt = "www17736123780eeeee 7377091 ddddsssss7777777";
//找到的成功匹配的集合
MatchCollection mc = Regex.Matches(txt, @"\d{7,}");
foreach (Match m in mc)
{
Console.WriteLine(m.Value);
}
