/// <summary>
/// 检查输入是否为ip地址字符串
/// </summary>
/// <param name="input">输入字符串</param>
/// <returns></returns>
private static bool IsIPAddress(string input)
{
    //原作者表达式@"^(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])$"
    return Regex.IsMatch(input, @"^(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])((\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])){3}|(\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])){5})$");
}

static void Main(string[] args)
{
    bool bt = IsIPAddress("192.168.0.0");
    bt = IsIPAddress("192.168.2.3.1.1");
    bt = IsIPAddress("bd5.168.2.1");
    bt = IsIPAddress("192.168.254.10");
    bt = IsIPAddress("192.168.254.10.1.1.1.1");
    bt = IsIPAddress("192.168.254.10.1.1.1");