正则表达式不验证域名

Question

I have this utility function as follows:

   public bool IsValidDomainName(string strIn)
        {
            return Regex.IsMatch(strIn, @"^([a-zA-Z0-9]+(\.[a-zA-Z0-9]+)+.*)$");
        }

This expression works using modelbinding validation in MVC:

[RegularExpression(@"^([a-zA-Z0-9]+(\.[a-zA-Z0-9]+)+.*)$", ErrorMessage = "Please enter valid website address")]

So my question is why is my utility function failing?

Update:

 public class RegexUtilities
    {
        bool invalid;

        public bool IsValidEmail(string strIn)
        {
            invalid = false;
            if (String.IsNullOrEmpty(strIn))
                return false;

            // Use IdnMapping class to convert Unicode domain names.
            strIn = Regex.Replace(strIn, @"(@)(.+)$", DomainMapper);
            if (invalid)
                return false;

            // Return true if strIn is in valid e-mail format.
            return Regex.IsMatch(strIn,
                                 @"^(?("")(""[^""]+?""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +
                                 @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9]{2,17}))$",
                                 RegexOptions.IgnoreCase);
        }

        public bool IsValidDomainName(string strIn)
        {
            return Regex.IsMatch(strIn, @"^([a-zA-Z0-9]+(\.[a-zA-Z0-9]+)+.*)$");
        }

        private string DomainMapper(Match match)
        {
            // IdnMapping class with default property values.
            IdnMapping idn = new IdnMapping();

            string domainName = match.Groups[2].Value;
            try
            {
                domainName = idn.GetAscii(domainName);
            }
            catch (ArgumentException)
            {
                invalid = true;
            }
            return match.Groups[1].Value + domainName;
        }
    }

Answer 1

Try this:

If you want to force prefixing the protocol http://, https:// etc.

^(http://|https://|ftp://)\w+\.\w+.*$

If you don't want to force prefixing the protocol http://, https:// etc.

^(http://|https://|ftp://)?\w+\.\w+.*$