Merging 2 Text Files in C#

Question

Firstly, i\'d just like to mention that I\'ve only started learning C# a few days ago so my knowledge of it is limited.

I\'m trying to create a program that will par

Answer 1

try this method. You can receive three paths. File 1, File 2 and File output.

public void MergeFiles(string pathFile1, string pathFile2, string pathResult)
{
    File.WriteAllText(pathResult, File.ReadAllText(pathFile1) + File.ReadAllText(pathFile2));
}

If the pathResult file exists, the WriteAllText method will overwrite it. Remember to include System.IO namespace.

Important: It is not recommended for large files! Use another options available on this thread.

Answer 2

Using a FileInfo extension you could merge one or more files by doing the following:

public static class FileInfoExtensions
{
  public static void MergeFiles(this FileInfo fi, string strOutputPath , params string[] filesToMerge)
  {
    var fiLines = File.ReadAllLines(fi.FullName).ToList();
    fiLines.AddRange(filesToMerge.SelectMany(file => File.ReadAllLines(file)));
    File.WriteAllLines(strOutputPath, fiLines.ToArray());
  }
}

Usage

  FileInfo fi = new FileInfo("input");
  fi.MergeFiles("output", "File2", "File3");

Answer 3

To combine the two files content in an one merged file line by line you could substitute your Combination() code with this

string[] file1 = File.ReadAllLines("*DIRECTORY*\FIRSTFILE.txt");
string[] file2 = File.ReadAllLines("*DIRECTORY*\SECONDFILE.txt");

using (StreamWriter writer = File.CreateText(@"*DIRECTORY*\FINALOUTPUT.txt"))
{
    int lineNum = 0;
    while(lineNum < file1.Length || lineNum < file2.Length)
    {
        if(lineNum < file1.Length)
            writer.WriteLine(file1[lineNum]);
        if(lineNum < file2.Length)
            writer.WriteLine(file2[lineNum]);
        lineNum++;
    }
}

This assumes that the two files don't contains the same number of lines.

Answer 4

If your input files are quite large and you run out of memory, you could also try wrapping the two readers like this:

        using (StreamWriter writer = File.CreateText(@"*DIRECTORY*\FINALOUTPUT.txt"))
        {
            using (StreamReader reader1 = File.OpenText(@"*DIRECTORY*\FIRSTFILE.txt"))
            {
                using (StreamReader reader2 = File.OpenText(@"*DIRECTORY*\SECONDFILE.txt"))
                {
                    string line1 = null;
                    string line2 = null;
                    while ((line1 = reader1.ReadLine()) != null)
                    {
                        writer.WriteLine(line1);
                        line2 = reader2.ReadLine();
                        if(line2 != null)
                        {
                            writer.WriteLine(line2);
                        }
                    }
                }
            }
        }

Still, you have to have an idea how many lines you have in your input files, but I think it gives you the general idea to proceed.