//This is a answer for: http://stackoverflow.com/questions/33943428/return-dictionary-value-if-key-substring-exist/33943514#33943514

​

using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    private static readonly Dictionary<string, string> _ipAddressesDictionary = new Dictionary<string, string>()

    {

           {"ip.qwer4.abc5.somename", "6x.x.00.xx"},

           {"ip.qwer4.abc5.somename.co", "5x.x.00.xx"},

           {"ip.qwer3.abc1.somename", "4x.3.xx.xx"},

           {"ip.qwer3.abc1.somename.com.mx", "3x.x.00.xx"},

           {"ip.qwer5.abc1.somename.com.br", "2x.x.00.xx"},

           {"ip.qwer6.abc1.somename.co.uk", "1x.x.00.xx"},

    };

    public static void Main()

    {

        Console.WriteLine("--first");

        Console.WriteLine(LookupByPrefix("abc1.somename.co.uk"));

        Console.WriteLine("--many abc1.somename.com");

        string[] many = LookupByPrefixMany("abc1.somename.com");

        foreach(string ip in many)

            Console.WriteLine(ip);

        Console.WriteLine("--many abc1");

        many = LookupByPrefixMany("abc1.euroname.co.uk");

        foreach(string ip in many)

            Console.WriteLine(ip);

    }

    public static string LookupByPrefix(string domainName)

    {

        string[] dotDomains = domainName.Split('.');

        for(int matchCount = dotDomains.Length; matchCount > 0; matchCount--)

        {

            string[] ret = LookUpPeerIpMany(string.Join(".", dotDomains.Take(matchCount)));

            if(ret != null && ret.Length > 0) return ret.SingleOrDefault();

        }

        return null;

    }

    public static string[] LookupByPrefixMany(string domainName)

    {

        string[] dotDomains = domainName.Split('.');

        for(int matchCount = dotDomains.Length; matchCount > 0; matchCount--)

        {

            string[] ret = LookUpPeerIpMany(string.Join(".", dotDomains.Take(matchCount)));

            if(ret != null && ret.Length > 0) return ret;

        }

        return null;

    }

    public static string[] LookUpPeerIpMany(string deviceName)

    {

        return _ipAddressesDictionary

               .Where(q=>q.Key.Contains(deviceName)).Select(q=>q.Value).ToArray();

    }

}