using System;using System.Diagnostics;using System.IO;

​

​

public class Program

{

    public static void Main()

    {

        string path = @"C:\test.txt",filename = ""; 

        Stopwatch x1 = new Stopwatch();

        x1.Start(); 

            filename = path.Substring(path.LastIndexOf("\\") + 1);      

        x1.Stop();

        Console.Write("x1 "+filename+" "); Console.WriteLine(x1.ElapsedTicks+" ticks");         

        Stopwatch x2 = new Stopwatch(); 

        x2.Start(); 

            filename = filename = Path.GetFileName(path);       

        x2.Stop();      

        Console.Write("x2 "+filename+" "); Console.WriteLine(x2.ElapsedTicks+" ticks");         

        Stopwatch x3 = new Stopwatch();

        x3.Start();

            var arr = path.ToCharArray();

            Array.Reverse(arr);

            string rpath = new string(arr);

            int pos = rpath.IndexOf('\\'); 

            filename = rpath.Substring(0, pos); 

            arr = filename.ToCharArray();

            Array.Reverse(arr);

            filename = new string(arr);

        x3.Stop();

        Console.Write("x3 "+filename+" "); Console.WriteLine(x3.ElapsedTicks+" ticks");         

        Stopwatch x4 = new Stopwatch();

        x4.Start(); 

            filename = path.Substring(path.LastIndexOf('\\') + 1);      

        x4.Stop();      

        Console.Write("x4 "+filename+" "); Console.WriteLine(x4.ElapsedTicks+" ticks");         

    }

}

​