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Home Forums How do you merge multiple text files into a single file? – MindStick
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1 Answers

Anubhav Sharma
Anubhav Sharma 22 May 2025
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To merge multiple text files into a single file in C#, you can use System.IO to read each file and append its content to the target file. Here's how:

Basic Example: Merge All .txt Files in a Folder

using System.IO;

string sourceDirectory = @"C:\TextFiles";
string outputFile = @"C:\Merged\combined.txt";

// Get all .txt files in the folder
var files = Directory.GetFiles(sourceDirectory, "*.txt");

// Merge into one file
using (var output = File.CreateText(outputFile))
{
    foreach (var file in files)
    {
        string content = File.ReadAllText(file);
        output.WriteLine(content);     // Write file content
        output.WriteLine();            // Optional: blank line between files
    }
}

Variation: Append Instead of Overwriting

If you want to append to an existing file:

foreach (var file in files)
{
    File.AppendAllText(outputFile, File.ReadAllText(file) + Environment.NewLine);
}

Optional Enhancements

Add File Headers

foreach (var file in files)
{
    var fileName = Path.GetFileName(file);
    File.AppendAllText(outputFile, $"--- {fileName} ---{Environment.NewLine}");
    File.AppendAllText(outputFile, File.ReadAllText(file) + Environment.NewLine);
}

Sort Files by Name or Date

var sortedFiles = Directory.GetFiles(sourceDirectory, "*.txt")
    .Select(f => new FileInfo(f))
    .OrderBy(f => f.Name) // or .CreationTime
    .Select(f => f.FullName);

Summary

Operation Code/Method
Read content File.ReadAllText(path)
Write or create file File.CreateText(path)
Append to file File.AppendAllText(path, ...)
Merge with headers Add file name before writing
Handle large files Stream line by line with StreamReader/Writer
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