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CompressionMode Enumeration

Specifies whether to compress or decompress the underlying stream.

Namespace:  System.IO.Compression
Assembly:  System (in System.dll)

'Declaration
Public Enumeration CompressionMode
'Usage
Dim instance As CompressionMode

Member nameDescription
Supported by the .NET Compact FrameworkSupported by the XNA FrameworkDecompressDecompresses the underlying stream.
Supported by the .NET Compact FrameworkSupported by the XNA FrameworkCompressCompresses the underlying stream.

This enumeration is used with the GZipStream and DeflateStream classes.

The following code example uses the CompressionMode enumeration with the GZipStream class to compress and decompress a file.

Imports System.IO
Imports System.IO.Compression
Module Module1

    Sub Main()
        ' Path to directory of files to compress. 
        Dim dirpath As String = "c:\users\public\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 *.gz files in the directory. 
        For Each fi As FileInfo In di.GetFiles("*.gz")
            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 <> ".gz" Then 
                ' Create the compressed file. 
                Using outFile As FileStream = File.Create(fi.FullName + ".gz")
                    Using Compress As GZipStream = New GZipStream(outFile, CompressionMode.Compress)
                        ' Copy the source file into the compression stream. 
                        Dim buffer As Byte() = New Byte(4096) {}
                        Dim numRead As Integer
                        numRead = inFile.Read(buffer, 0, buffer.Length)
                        Do While numRead <> 0
                            Compress.Write(buffer, 0, numRead)
                            numRead = inFile.Read(buffer, 0, buffer.Length)
                        Loop

                        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.gz. 
            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 GZipStream = New GZipStream(inFile, CompressionMode.Decompress)
                    ' Copy the compressed file into the decompression stream. 
                    Dim buffer As Byte() = New Byte(4096) {}
                    Dim numRead As Integer
                    numRead = Decompress.Read(buffer, 0, buffer.Length)
                    Do While numRead <> 0
                        outFile.Write(buffer, 0, numRead)
                        numRead = Decompress.Read(buffer, 0, buffer.Length)
                    Loop
                    Console.WriteLine("Decompressed: {0}", fi.Name)

                End Using 
            End Using 
        End Using 
    End Sub 
End Module

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0

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