private bool IsValidCNIC(string cnic)
{
    Regex check = new Regex(@"^[0-9]{5}-[0-9]{7}-[0-9]{1}$");
    bool valid = false;
    valid = check.IsMatch(cnic);
    return valid;
}

here is code I copied From Stack But I don't Know How to Call in CNIC input tag in HTml