GZipStream Constructor (Stream, CompressionMode)

 

Initializes a new instance of the GZipStream class by using the specified stream and compression mode.

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

public GZipStream(
	Stream stream,
	CompressionMode mode
)

Parameters

stream
Type: System.IO.Stream

The stream the compressed or decompressed data is written to.

mode
Type: System.IO.Compression.CompressionMode

One of the enumeration values that indicates whether to compress or decompress the stream.

Exception Condition
ArgumentNullException

stream is null.

ArgumentException

mode is not a valid CompressionMode enumeration value.

-or-

CompressionMode is Compress and CanWrite is false.

-or-

CompressionMode is Decompress and CanRead is false.

By default, GZipStream owns the underlying stream, so closing the stream parameter also closes the underlying stream. Note that the state of the underlying stream can affect the usability of the stream. Also, no explicit checks are performed, so no additional exceptions are thrown when the new instance is created.

If an instance of the GZipStream class is created with the mode parameter equal to Compress and no further action occurs, the stream will appear as a valid, empty compressed file.

By default, the compression level is set to Optimal when the compression mode is Compress.

The following example initializes a new instance of the GZipStream class with mode set to Compress. This example is part of a larger example provided for the GZipStream class.

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

namespace zip
{
    public class Program
    {
        private static string directoryPath = @"c:\temp";
        public static void Main()
        {
            DirectoryInfo directorySelected = new DirectoryInfo(directoryPath);
            Compress(directorySelected);

            foreach (FileInfo fileToDecompress in directorySelected.GetFiles("*.gz"))
            {
                Decompress(fileToDecompress);
            }
        }

        public static void Compress(DirectoryInfo directorySelected)
        {
            foreach (FileInfo fileToCompress in directorySelected.GetFiles())
            {
                using (FileStream originalFileStream = fileToCompress.OpenRead())
                {
                    if ((File.GetAttributes(fileToCompress.FullName) & 
                       FileAttributes.Hidden) != FileAttributes.Hidden & fileToCompress.Extension != ".gz")
                    {
                        using (FileStream compressedFileStream = File.Create(fileToCompress.FullName + ".gz"))
                        {
                            using (GZipStream compressionStream = new GZipStream(compressedFileStream, 
                               CompressionMode.Compress))
                            {
                                originalFileStream.CopyTo(compressionStream);

                            }
                        }
                        FileInfo info = new FileInfo(directoryPath + "\\" + fileToCompress.Name + ".gz");
                        Console.WriteLine("Compressed {0} from {1} to {2} bytes.",
                        fileToCompress.Name, fileToCompress.Length.ToString(), info.Length.ToString());
                    }

                }
            }
        }

        public static void Decompress(FileInfo fileToDecompress)
        {
            using (FileStream originalFileStream = fileToDecompress.OpenRead())
            {
                string currentFileName = fileToDecompress.FullName;
                string newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length);

                using (FileStream decompressedFileStream = File.Create(newFileName))
                {
                    using (GZipStream decompressionStream = new GZipStream(originalFileStream, CompressionMode.Decompress))
                    {
                        decompressionStream.CopyTo(decompressedFileStream);
                        Console.WriteLine("Decompressed: {0}", fileToDecompress.Name);
                    }
                }
            }
        }
    }
}

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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