Reading text file inside the Folder in c#

If you mean the latest by creation date, then try this:

using System;
using System.IO;
using System.Linq;

class Program
{
   static void Main()
   {
       var di = new DirectoryInfo(@"c:\Main");
       string search = "test*.txt";
       FileInfo latest = di.GetFiles(search).OrderBy(fi => fi.CreationTime).Last();
       string text = File.ReadAllText(latest.FullName);
       Console.WriteLine(text);
       Console.ReadKey();
   }
}