GZipStream

This class compresses data. It saves data efficiently—such as in compressed log files. GZIP has a file header, while DEFLATE does not.

We develop a utility method in the C# language that uses the System.IO.Compression namespace. It creates GZIP files. It writes them to the disk.

GZipStream example

We use the .NET built-in methods. Compression and decompression using GZIP is common in any programming language. GZIP is widely used on the Internet.

using System.IO;
using System.IO.Compression;
using System.Text;

class Program
{
    static void Main()
    {
        try
        {
            // Starting file is 26,747 bytes.
            string anyString = File.ReadAllText("TextFile1.txt");

            // Output file is 7,388 bytes.
            CompressStringToFile("new.gz", anyString);
        }
        catch
        {
            // Could not compress.
        }
    }

    public static void CompressStringToFile(string fileName, string value)
    {
        // Part 1: write string to temporary file.
        string temp = Path.GetTempFileName();
        File.WriteAllText(temp, value);

        // Part 2: read file into byte array buffer.
        byte[] b;
        using (FileStream f = new FileStream(temp, FileMode.Open))
        {
            b = new byte[f.Length];
            f.Read(b, 0, (int)f.Length);
        }

        // Part 3: use GZipStream to write compressed bytes to target file.
        using (FileStream f2 = new FileStream(fileName, FileMode.Create))
        using (GZipStream gz = new GZipStream(f2, CompressionMode.Compress, false))
        {
            gz.Write(b, 0, b.Length);
        }
    }
}
Starting file is 26,747 bytes.
Output file is 7,388 bytes.

DeflateStream

With DeflateStream we can output a deflate file. A GZIP file contains a DEFLATE body. With GZIP we have an additional header.

using System.IO;
using System.IO.Compression;

class Program
{
    static void Main()
    {
        CompressWithDeflate("C:\\programs\\example.txt", "C:\\programs\\deflate-output");
    }

    static void CompressWithDeflate(string inputPath, string outputPath)
    {
        // Read in input file.
        byte[] b = File.ReadAllBytes(inputPath);

        // Write compressed data with DeflateStream.
        using (FileStream f2 = new FileStream(outputPath, FileMode.Create))
        using (DeflateStream deflate = new DeflateStream(f2, CompressionMode.Compress, false))
        {
            deflate.Write(b, 0, b.Length);
        }
    }
}

Notes, reliable

CompressStringToFile is tested and reliable. I have used it in deployed applications. It however can be slow—caching, or other optimizations may be needed.

A summary

We used GZipStream to compress to a file with an underlying FileStream. More complex methods are available for compression. This example alone does not meet most requirements.