using System;

using System.Text.RegularExpressions;

​

public class Program //dotnetfiddle.net/SignUp

{

    public static void Main()

    {

        var searchQuery="bent123@hotmail.com";

        var a = @"(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|""(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*"")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9]))\.){3}(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])";

        var s = Regex.Replace(searchQuery, a, m =>

        {

            //Console.WriteLine(m.Groups[0].Value);

            return @""""+m.Groups[0].Value+@"""";

        }   );

        Console.WriteLine(s);

        searchQuery="bent123@hotmail.com jim@internet.org";

        s = Regex.Replace(searchQuery, a, m =>

        {

            //Console.WriteLine(m.Groups[0].Value);

            return @""""+m.Groups[0].Value+@"""";

        }   );

        Console.WriteLine(s);

​

        searchQuery="bent123@hotmail.com jim@internet.org 234324234324324";

        s = Regex.Replace(searchQuery, a, m =>

        {

            //Console.WriteLine(m.Groups[0].Value);

            return @""""+m.Groups[0].Value+@"""";

        }   );

        Console.WriteLine(s);

​

        searchQuery=@"bent123@hotmail.com jim@internet.org 234324234324324 some other test ""power test""";

        s = Regex.Replace(searchQuery, a, m =>

        {

            //Console.WriteLine(m.Groups[0].Value);

            return @""""+m.Groups[0].Value+@"""";

        }   );

        Console.WriteLine(s);

​

        searchQuery=@"bent123@hotmail.com jim@internet.org 234324234324324 some other test ""power test"" ""mismatched quote at end someone@Qinternet.com""";

        s = Regex.Replace(searchQuery, a, m =>

        {

            //Console.WriteLine(m.Groups[0].Value);

            return @""""+m.Groups[0].Value+@"""";

        }   );

        Console.WriteLine(s);

​

        searchQuery=@"bent123@hotmail.com jim@internet.org 234324234324324 some other test ""power test"" ""mismatched quote"" at end someone@internet.com some""";

        s = Regex.Replace(searchQuery, a, m =>

        {

            //Console.WriteLine(m.Groups[0].Value);

            return @""""+m.Groups[0].Value+@"""";

        }   );

        Console.WriteLine(s);

​

    }

}