Email Address Verification

Question

So what I am trying to do is to verify an Email Address that the user will input himself.

Microsoft developer network offer a sample code of how to verify email address in the following link: http://msdn.microsoft.com/en-us/library/01escwtf(v=vs.110).aspx

Anyway I just copied the code and tried to use it. However I keep getting this error:

The type or namespace name 'IdnMapping' could not be found (are you missing a using directive or an assembly reference?)

I could not find any similar issue online and I can't think of what would cause this error.

Of course, what would first come to our mind when we see such an error is that we forgot to include something.

However I included whatever is needed as in the page above and as I will be showing in my code. So I really can't even understand the nature of the problem itself to start searching for a possible solution.

My Code:

using System;
using System.Globalization;
using System.Text.RegularExpressions;

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

        // Use IdnMapping class to convert Unicode domain names. 
        try
        {
            strIn = Regex.Replace(strIn, @"(@)(.+)$", this.DomainMapper,
                                  RegexOptions.None, TimeSpan.FromMilliseconds(200));
        }
        catch (RegexMatchTimeoutException)
        {
            return false;
        }

        if (invalid)
            return false;

        // Return true if strIn is in valid e-mail format. 
        try
        {
            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]{2,24}))$",
                  RegexOptions.IgnoreCase, TimeSpan.FromMilliseconds(250));
        }
        catch (RegexMatchTimeoutException)
        {
            return false;
        }
    }

    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;
    }

Any suggestions on how to solve this issue or at least understanding the nature of the issue. Thanks in advance :)

Answer 1

Try this RFC822-compliant method:

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.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(
?:\r\n)?[ \t])*))*)?;\s*)".Replace(Environment.NewLine, "");

Then you can do this:

    var emailRegex = new Regex(text);

    var isValid = emailRegex.IsMatch("foo@bar.com");

Seriously this is correct.

Answer 2

Using the MailAddress class, here is a nice a piece of code. The reason is that someone else has already done the Regex for you.

    public bool IsValid(string emailaddress)
    {
        try
        {
            MailAddress m = new MailAddress(emailaddress);
            return true;
        }
        catch (FormatException)
        {
            return false;
        }
    }

Answer 3

Ok I just found this one right now, it seems to be working for me and I just wanted to share it.

private bool IsValidEmail(string emailAddress)
{
        // Return true if emailAddress is in valid e-mail format.
        return Regex.IsMatch(emailAddress, @"^([0-9a-zA-Z]([-\.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$");
}

Answer 4

It seems the class doesn't exist on .NET for Windows Phone.

This MSDN page says it only exists on .NET Framework 2.0+ and .NET Framework Client Profile 3.5 SP1+.