validating an Email ID?

Question

 

how to validate an email id using general coding in visual C#. pls can any one help me...

Answer 1

You can use the following code for validating an email through C#

 public static Boolean IsValidEmail(string email)

        {

            try

            {

                string strRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +

                               @"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" +

                               @".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";

                

                System.Text.RegularExpressions.Regex exp = new System.Text.RegularExpressions.Regex(strRegex);

                System.Text.RegularExpressions.Match m;

                m = exp.Match(email, 0);

                return m.Success;

            }

Answer 2

How would you define validating?

- Does it have to mach a certain format? (Search the web for RFC822 compliant regex)
- Does the have to be deliverable?
- Has the user that provided the address to confirm that he actually is able to read incoming messages?

Answer 3

 

Hi

 

The best way is to use regex, see below

 

Code Snippet

        using System.Text.RegularExpressions;

 

        private void cmdValidateEmail_Click(object sender, EventArgs e)

        {

            if (isValidEmail(txtEmail.Text))

            {

                MessageBox.Show("Valid Email");

            }

            else

            {

                MessageBox.Show("Invalid Email");

            }

        }

 

        public static bool isValidEmail(string inputEmail)

        {

            string strRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +

                  @"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" +

                  @".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";

            Regex re = new Regex(strRegex);

            if (re.IsMatch(inputEmail))

                return (true);

            else

                return (false);

        }

 

 

Hope this helps.

Answer 4

Additional Information

 

The next level of validation, we can attempt is to make a negotiation with the SMTP server and validate. Some mail servers respond even to VRFY and/or RCPT SMTP commands as to whether the email address is valid or not. But servers which are very strictly configured of not disclosing non-existing addresses, will always acknowledge any junk addresses in their domain and would bounce them on their own later. We need to tackle each of the following.

Validating SMTP Network Connection

Code Snippet
string[] host = (address.Split('@'));
string hostname = host[1];
 
IPHostEntry IPhst = Dns.Resolve(hostname);
IPEndPoint endPt = new IPEndPoint(IPhst.AddressList[0], 25);
Socket s = new Socket(endPt.AddressFamily,
SocketType.Stream, ProtocolType.Tcp);
s.Connect(endPt);
 
 

This step will throw an exception, if the domain is not valid, so that you can flag that the email address is invalid.

Answer 5

And what if the MX record points to a different host?

 (Anyway, as posted already, more details regarding 'validation' are required)


Btw, coincidentally i read http://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx today...

Answer 6

In my company we use EmailVerify.NET (http://www.emailverify.net), a Microsoft .NET component which supports e-mail syntax checking, domain MX test and mailbox validation too.
E-mail validation up to the mailbox level is easy as writing the following code block:

var verifier = new EmailVerifier();
var result = verifier.Verify("[e-mail]", VerificationLevel.Mailbox);

if (result.IsSuccess)
{
   // Go on, send the message
}

Additional code samples can be found here.
From their home page:

EmailVerify.NET is a powerful .NET component which verifies email addresses using various techniques, including:

• Syntax verification, according to RFC 2821 and RFC 2822
• MX record lookup
• Disposable email address (DEA) validation
• SMTP availability check
• Mailbox existence check, with greylisting support
• Catch-all test

It is completely written in managed code (C#) and is compliant with the Common Language Specification (CLS), so it can be used with any other .NET language, including VB.NET, C++/CLI, J#, IronPython, IronRuby and F#.

The price for this component is very small (less than 50 bucks) and their support is one of the greatest I've ever found for a small software company like they are.
Hope this helps.