C#

using System;
using System.IO;
using System.Text;
using System.Collections.Generic;

class MainClass
{
    public static void Main(string[] args)
    {
        string inFile, filePath;
        string line;


        DirectoryInfo di = new DirectoryInfo(@"D:\a\");
        FileInfo[] files = di.GetFiles("*.txt");
        Console.WriteLine("Input file name to open!");
        Console.WriteLine("Sample: d:\\filename.txt");
        inFile = Convert.ToString(Console.ReadLine());
        StreamReader sr = File.OpenText(inFile);
        line = sr.ReadLine();
        foreach (FileInfo fi in files)
        {
            inFile = fi.FullName;
           
            Console.WriteLine();
            Console.WriteLine("Successful file open!...");
            Console.WriteLine();
            Console.WriteLine("Input file name to save!");
            Console.WriteLine("sample: d:\\filename.txt");
            filePath = Console.ReadLine();
            FileStream file = new FileStream(filePath, FileMode.Create);
            StreamWriter sw = new StreamWriter(file);
            List<string> lines = new List<string>();

            while ((line = sr.ReadLine()) != null)
            {
                lines.Add(line);
            }
            try
            {
                int numberOne = Int32.Parse(lines[0]);
                int numberTwo = Int32.Parse(lines[1]);
                int numberThree = Int32.Parse(lines[2]);
                int x = numberOne + numberTwo + numberThree;
                sw.WriteLine(x);
            }
            catch { }
            sw.Close();
            sr.Close();
        }

    }
}
        </string></string>

System.Diagnostic.Process.Start("filename");

public static string GetHTMLStringWin(string url)
     {
         StringBuilder html = new StringBuilder();
         string htmlToRet = null;
         try
         {
             //-- Make an HTTP web request to retrieve content --//
             HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
             request.Timeout = 30000;
             HttpWebResponse response = (HttpWebResponse)request.GetResponse();
             Stream htmlStream = response.GetResponseStream();
             string temp = null;
             byte[] buffer = new byte[9000];
             int counter = 0;

             do
             {
                 counter = htmlStream.Read(buffer, 0, buffer.Length);
                 if (counter != 0)
                 {
                     //-- The encoding is set to UTF-8 --//
                     temp = Encoding.GetEncoding("windows-1252").GetString(buffer, 0, counter);
                     //temp = Encoding.GetEncoding("iso-8859-1").GetString(buffer, 0, counter);
                     html.Append(temp);
                 }

             }
             while (counter > 0);

             htmlToRet = html.ToString();
         }
         catch
         {
             htmlToRet = null;
             //-- Add Exception Logic here --//
         }
         return htmlToRet;
     }