using System;

using System.IO; 

using System.Diagnostics; 

​

public static class StringExtension

{    

        /// <summary>

        /// Get filename extension, not ext of . only returns empty string, mirrors Path.GetExtension not try/catch issues by metadataconsulting.blogspot.com

        /// </summary>

        /// <param name="s"></param>

        /// <returns></returns>

        public static string GetFileNameExtension(this string s)

        {

            string ext = "";

            int fileExtPos = s.LastIndexOf('.');

            if (fileExtPos > s.LastIndexOf('\\'))

            {

                ext = s.Substring(fileExtPos, s.Length - fileExtPos);

                if (ext.Length <= 1) ext = "";

            }

            else

                ext = "";

            return ext;

        }

}

public class Program

{

    public static string GetFileExtStringRef(ref string file) {

        //string ext="";

        int fileExtPos = file.LastIndexOf('.');

        if (fileExtPos >  file.LastIndexOf('\\'))

            return file.Substring(fileExtPos, file.Length - fileExtPos);

        else

            return "";

    }

    public static void Main()

    {

        //string file = @"c:\foo\bar.cat\cheese.exe.e.x";

        string file = "cheese.log.txt";

        Console.WriteLine("Inline String Manipulation"); 

        Stopwatch s = new Stopwatch();

        s.Start(); 

            string ext = ""; 

            int fileExtPos = file.LastIndexOf('.');

            if (fileExtPos > file.LastIndexOf('\\'))

            {

                ext = file.Substring(fileExtPos, file.Length - fileExtPos);

                if (ext.Length <= 1) ext = "";

            }

            else

                ext = "";

        s.Stop();

        Console.WriteLine(ext+ " in ticks "+ s.ElapsedTicks); 

        Console.WriteLine("Native Path.IO Get Extension"); 

        s.Reset();

        s.Start();      

            ext = Path.GetExtension(file); 

        s.Stop(); 

        Console.WriteLine(ext+ " in ticks "+ s.ElapsedTicks); 

​

        Console.WriteLine("String Extension call"); 

        s.Reset();

        s.Start();      

            ext = file.GetFileNameExtension();

        s.Stop(); 

        Console.WriteLine(ext+ " in ticks "+ s.ElapsedTicks); 

​

        Console.WriteLine("By Ref Method Call");        

        s.Reset();

        s.Start();      

            ext = GetFileExtStringRef(ref file);

        s.Stop(); 

        Console.WriteLine(ext+ " in ticks "+ s.ElapsedTicks); 

    }

}