Question

Here’s the scenario.

I have a text file(alpha), single column, with a bunch of items.

My 2nd file is a csv(delta) with 4 columns.

I have to have the alpha compare again the delta and create a new file (omega) in which anything that alpha matched delta, it would export only the first two columns from delta into a new .txt file.

Example:
(Alpha)
BeginID

(delta):
BeginID,Muchmore,Info,Exists

(Omega):
BeginID,Muchmore

This document will probably have 10k lines it in. Thanks for the help!

Answer 1

Here’s a rough cut way of doing the task you need:

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string alphaFilePath = @"C:\Documents and Settings\Jason\My Documents\Visual Studio 2008\Projects\Compte Two Files\Compte Two Files\ExternalFiles\Alpha.txt";

            List<string> alphaFileContent = new List<string>();

            using (FileStream fs = new FileStream(alphaFilePath, FileMode.Open))
            using(StreamReader rdr = new StreamReader(fs))
            {
                while(!rdr.EndOfStream)
                {
                    alphaFileContent.Add(rdr.ReadLine());
                }
            }

            string betaFilePath = @"C:\Beta.csv";

            StringBuilder sb = new StringBuilder();


            using (FileStream fs = new FileStream(betaFilePath, FileMode.Open))
            using (StreamReader rdr = new StreamReader(fs))
            {
                while(! rdr.EndOfStream)
                {
                    string[] betaFileLine = rdr.ReadLine().Split(Convert.ToChar(","));

                    if (alphaFileContent.Contains(betaFileLine[0]))
                    {
                        sb.AppendLine(String.Format("{0}, {1}", betaFileLine[0], betaFileLine[1]));
                    }
                }


               }

using (FileStream fs = new FileStream(@"C:\Omega.txt", FileMode.Create))
            using (StreamWriter writer = new StreamWriter(fs))
            {
                writer.Write(sb.ToString());
            }

                Console.WriteLine(sb.ToString());
            }
        }
    }

Basically it reads a txt file, puts the contents in a list. Then it reads a csv file (assuming no columns) and matches the values to create a StringBuilder. In your code, substitute the StringBuilder with creating a new txt file.

EDIT: If you wish to have the code run in a button click, then put it in the button click handler (or a new routine and call that):

public void ButtonClick (Object sender, EventArgs e)
{
string alphaFilePath = @"C:\Documents and Settings\Jason\My Documents\Visual Studio 2008\Projects\Compte Two Files\Compte Two Files\ExternalFiles\Alpha.txt";

            List<string> alphaFileContent = new List<string>();

            using (FileStream fs = new FileStream(alphaFilePath, FileMode.Open))
            using(StreamReader rdr = new StreamReader(fs))
            {
                while(!rdr.EndOfStream)
                {
                    alphaFileContent.Add(rdr.ReadLine());
                }
            }

            string betaFilePath = @"C:\Beta.csv";

            StringBuilder sb = new StringBuilder();


            using (FileStream fs = new FileStream(betaFilePath, FileMode.Open))
            using (StreamReader rdr = new StreamReader(fs))
            {
                while(! rdr.EndOfStream)
                {
                    string[] betaFileLine = rdr.ReadLine().Split(Convert.ToChar(","));

                    if (alphaFileContent.Contains(betaFileLine[0]))
                    {
                        sb.AppendLine(String.Format("{0}, {1}", betaFileLine[0], betaFileLine[1]));
                    }
                }
            }

using (FileStream fs = new FileStream(@"C:\Omega.txt", FileMode.Create))
        using (StreamWriter writer = new StreamWriter(fs))
        {
            writer.Write(sb.ToString());
        }
    }