DeflateStream Class
.NET Framework Class Library
DeflateStream Class

Provides methods and properties for compressing and decompressing streams using the Deflate algorithm.

Namespace:  System.IO.Compression
Assembly:  System (in System.dll)
Visual Basic
Public Class DeflateStream _
    Inherits Stream
C#
public class DeflateStream : Stream
Visual C++
public ref class DeflateStream : public Stream
F#
type DeflateStream =  
    class
        inherit Stream
    end

This class represents the Deflate algorithm, an industry standard algorithm for lossless file compression and decompression. It uses a combination of the LZ77 algorithm and Huffman coding. Data can be produced or consumed, even for an arbitrarily long, sequentially presented input data stream, using only previously bound amount of intermediate storage. The format can be implemented readily in a manner not covered by patents. For more information, see RFC 1951. "DEFLATE Compressed Data Format Specification version 1.3."

This class does not inherently provide functionality for adding files to or extracting files from .zip archives.

The GZipStream class uses the gzip data format, which includes a cyclic redundancy check value for detecting data corruption. The gzip data format uses the same compression algorithm as the DeflateStream class.

The compression functionality in DeflateStream and GZipStream is exposed as a stream. Data is read in on a byte-by-byte basis, so it is not possible to perform multiple passes to determine the best method for compressing entire files or large blocks of data. The DeflateStream and GZipStream classes are best used on uncompressed sources of data. If the source data is already compressed, using these classes may actually increase the size of the stream.

The following example shows how to use the DeflateStream class to compress and decompress a directory of files.

Visual Basic
Imports System.IO
Imports System.IO.Compression
Module Module1

    Sub Main()
        ' Path to directory of files to compress.
        Dim dirpath As String = "c:\users\pubic\reports"

        Dim di As DirectoryInfo = New DirectoryInfo(dirpath)

        ' Compress the directory's files.
        For Each fi As FileInfo In di.GetFiles()
            Compress(fi)
        Next

        ' Decompress all *.cmp files in the directory.
        For Each fi As FileInfo In di.GetFiles("*.cmp")
            Decompress(fi)
        Next

    End Sub

    ' Method to compress.
    Private Sub Compress(ByVal fi As FileInfo)
        ' Get the stream of the source file.
        Using inFile As FileStream = fi.OpenRead()
            ' Compressing:
            ' Prevent compressing hidden and already compressed files.

            If (File.GetAttributes(fi.FullName) And FileAttributes.Hidden) _
                <> FileAttributes.Hidden And fi.Extension <> ".cmp" Then
                ' Create the compressed file.
                Using outFile As FileStream = File.Create(fi.FullName + ".cmp")
                    Using Compress As DeflateStream = New DeflateStream(outFile, _
                                                        CompressionMode.Compress)
                        ' Copy the source file into the compression stream.
                        inFile.CopyTo(Compress)

                        Console.WriteLine("Compressed {0} from {1} to {2} bytes.", _
                          fi.Name, fi.Length.ToString(), outFile.Length.ToString())

                    End Using
                End Using
            End If
        End Using
    End Sub

    ' Method to decompress.
    Private Sub Decompress(ByVal fi As FileInfo)
        ' Get the stream of the source file.
        Using inFile As FileStream = fi.OpenRead()
            ' Get orignial file extension, for example "doc" from report.doc.cmp.
            Dim curFile As String = fi.FullName
            Dim origName = curFile.Remove(curFile.Length - fi.Extension.Length)

            ' Create the decompressed file.
            Using outFile As FileStream = File.Create(origName)
                Using Decompress As DeflateStream = New DeflateStream(inFile, _
                                                        CompressionMode.Decompress)

                    ' Copy the decompression stream into the output file.
                    Decompress.CopyTo(outFile)
                    
                    Console.WriteLine("Decompressed: {0}", fi.Name)

                End Using
            End Using
        End Using
    End Sub
End Module
C#
using System;
using System.IO;
using System.IO.Compression;

public class Program
{

    public static void Main()
    {
        // Path to directory of files to compress and decompress.
        string dirpath = @"c:\users\public\reports";

        DirectoryInfo di = new DirectoryInfo(dirpath);

        // Compress the directory's files.
        foreach (FileInfo fi in di.GetFiles())
        {
            Compress(fi);
        }

        // Decompress all *.cmp files in the directory.
        foreach (FileInfo fi in di.GetFiles("*.cmp"))
        {
            Decompress(fi);
        }


    }

    public static void Compress(FileInfo fi)
    {
        // Get the stream of the source file.
        using (FileStream inFile = fi.OpenRead())
        {
            // Prevent compressing hidden and already compressed files.
            if ((File.GetAttributes(fi.FullName) & FileAttributes.Hidden)
                != FileAttributes.Hidden & fi.Extension != ".cmp")
            {
                // Create the compressed file.
                using (FileStream outFile = 
                        File.Create(fi.FullName + ".cmp"))
                {
                    using (DeflateStream Compress = 
                        new DeflateStream(outFile, 
                        CompressionMode.Compress))
                    {
                        // Copy the source file into 
                        // the compression stream.
                        inFile.CopyTo(Compress);

                        Console.WriteLine("Compressed {0} from {1} to {2} bytes.",
                        fi.Name, fi.Length.ToString(), outFile.Length.ToString());
                    }
                }
            }
        }
    }

    public static void Decompress(FileInfo fi)
    {
        // Get the stream of the source file.
        using (FileStream inFile = fi.OpenRead())
        {
            // Get original file extension, 
            // for example "doc" from report.doc.cmp.
            string curFile = fi.FullName;
            string origName = curFile.Remove(curFile.Length 
                    - fi.Extension.Length);

            //Create the decompressed file.
            using (FileStream outFile = File.Create(origName))
            {
                using (DeflateStream Decompress = new DeflateStream(inFile,
                    CompressionMode.Decompress))
                {
                        // Copy the decompression stream 
                        // into the output file.
                        Decompress.CopyTo(outFile);
                    
                    Console.WriteLine("Decompressed: {0}", fi.Name);
                }
            }
        }
    }
}
System..::.Object
  System..::.MarshalByRefObject
    System.IO..::.Stream
      System.IO.Compression..::.DeflateStream
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role not supported), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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DeflateStream does not handle ZIP files, but DotNetZip does.      cheeso   |   Edit   |   Show History

DeflateStream doesn't handle ZIP files, but DotNetZip does. You can use DotNetZip (http://dotnetzip.codeplex.com ), a free 3rd-party library, to create and read zip files from within any .NET application. . .

This code in C#, zips all the files in a specified directory.

using (ZipFile zip = new ZipFile())
{
zip.AddDirectory(@"MyDocuments\ProjectX", "ProjectX");
zip.Comment = "This zip was created at " + System.DateTime.Now.ToString("G") ;
zip.Save(zipFileToCreate);
}



This code in C#, unzips a zipfile:

      string unpackDirectory = "ExtractedFiles";
using (ZipFile zip1 = ZipFile.Read(zipToUnpack))
{
// here, we extract every entry, but we could extract conditionally
// based on entry name, size, date, checkbox status, etc.
foreach (ZipEntry e in zip1)
{
e.Extract(unpackDirectory, ExtractExistingFileAction.OverwriteSilently);
}
}


DotNetZip is free.

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