Develop Reference

How to Detect a Compressed File in C#

I'm trying to write a text search routine that scans a directory for a given wildcard file spec and scans the matches for a given search string. Everything works except for when I get to ZIP files. Here's the relevant code:
string fileText = File.ReadAllText(filePath);
foreach (string s in lstSearchStrings.Items)
{
int cnt = CountSubStrings(fileText, s);
lstCounts.Items.Add(cnt.ToString());
}
I know it only uses text-based routines so I probably need to change that. Any help in where to make changes / what to do would be appreciated!

You can use SharpZipLib to read inside zip files.
using ICSharpCode.SharpZipLib.Zip;
using (var zipFile = new ZipFile(#"test.zip"))
{
foreach (ZipEntry entry in zipFile)
{
Console.WriteLine(entry.Name);
}
}
First you detect zip files using extension. Then read those using above method.
string fileText = File.ReadAllText(entry.name);

Convert .zip file into byte array and re-create .zip from byte array

I have converted a .zip file into a byte[], and now I am trying to convert the byte[] back to the original .zip file. I am running out of the options that I have tried. Anyone give me a pointer how can I achieve this?

You want the System.IO.Compression.ZipArchive class:
using (ZipArchive zip = ZipFile.Open("test.zip", ZipArchiveMode.Create))
{
var entry = zip.CreateEntry("File Name.txt");
using (StreamWriter sw = new StreamWriter(entry.Open()))
{
sw.Write("Some Text");
}
}
using (ZipArchive zip = ZipFile.Open("test.zip", ZipArchiveMode.Read))
{
foreach (ZipArchiveEntry entry in zip.Entries)
{
using (StreamReader sr = new StreamReader(entry.Open()))
{
var result = sr.ReadToEnd();
}
}
}
You probably don't want to read in the raw zip file into a byte array first and then try to decompress it. Instead, access it through this helper method.
Note the use of ZipArchive.Entries to access the sub-files stored in the single zip archive; this tripped me up when first learning to use zip files.

Append text to existing Gzip file

I'm working on a log program, which would dump data into gzip archive.
The first entry would look like this:
using (var fs = File.OpenWrite(logFile))
{
using (var gs = new GZipStream(fs, CompressionMode.Compress))
{
using (var sw = new StreamWriter(gs))
{
sw.WriteLine(logEntry);
}
}
}
Now I want add other lines to that file without having to re-read all file content and than to re-write it in a way that the result can be read with a single GZipStream.
What is the best way to do that?

You can use gzlog.h and gzlog.c from the zlib distribution in the examples directory. They do exactly what you're looking for.

How to read data from a zip file without having to unzip the entire file

Is there anyway in .Net (C#) to extract data from a zip file without decompressing the complete file?
I possibly want to extract data (file) from the start of a zip file if the compression algorithm compress the file used was in a deterministic order.

With .Net Framework 4.5 (using ZipArchive):
using (ZipArchive zip = ZipFile.Open(zipfile, ZipArchiveMode.Read))
foreach (ZipArchiveEntry entry in zip.Entries)
if(entry.Name == "myfile")
entry.ExtractToFile("myfile");
Find "myfile" in zipfile and extract it.

DotNetZip is your friend here.
As easy as:
using (ZipFile zip = ZipFile.Read(ExistingZipFile))
{
ZipEntry e = zip["MyReport.doc"];
e.Extract(OutputStream);
}
(you can also extract to a file or other destinations).
Reading the zip file's table of contents is as easy as:
using (ZipFile zip = ZipFile.Read(ExistingZipFile))
{
foreach (ZipEntry e in zip)
{
if (header)
{
System.Console.WriteLine("Zipfile: {0}", zip.Name);
if ((zip.Comment != null) && (zip.Comment != ""))
System.Console.WriteLine("Comment: {0}", zip.Comment);
System.Console.WriteLine("\n{1,-22} {2,8} {3,5} {4,8} {5,3} {0}",
"Filename", "Modified", "Size", "Ratio", "Packed", "pw?");
System.Console.WriteLine(new System.String('-', 72));
header = false;
}
System.Console.WriteLine("{1,-22} {2,8} {3,5:F0}% {4,8} {5,3} {0}",
e.FileName,
e.LastModified.ToString("yyyy-MM-dd HH:mm:ss"),
e.UncompressedSize,
e.CompressionRatio,
e.CompressedSize,
(e.UsesEncryption) ? "Y" : "N");
}
}
Edited To Note: DotNetZip used to live at Codeplex. Codeplex has been shut down. The old archive is still available at Codeplex. It looks like the code has migrated to Github:
https://github.com/DinoChiesa/DotNetZip. Looks to be the original author's repo.
https://github.com/haf/DotNetZip.Semverd. This looks to be the currently maintained version. It's also packaged up an available via Nuget at https://www.nuget.org/packages/DotNetZip/

Something like this will list and extract the files one by one, if you want to use SharpZipLib:
var zip = new ZipInputStream(File.OpenRead(#"C:\Users\Javi\Desktop\myzip.zip"));
var filestream = new FileStream(#"C:\Users\Javi\Desktop\myzip.zip", FileMode.Open, FileAccess.Read);
ZipFile zipfile = new ZipFile(filestream);
ZipEntry item;
while ((item = zip.GetNextEntry()) != null)
{
Console.WriteLine(item.Name);
using (StreamReader s = new StreamReader(zipfile.GetInputStream(item)))
{
// stream with the file
Console.WriteLine(s.ReadToEnd());
}
}
Based on this example: content inside zip file

Here is how a UTF8 text file can be read from a zip archive into a string variable (.NET Framework 4.5 and up):
string zipFileFullPath = "{{TypeYourZipFileFullPathHere}}";
string targetFileName = "{{TypeYourTargetFileNameHere}}";
string text = new string(
(new System.IO.StreamReader(
System.IO.Compression.ZipFile.OpenRead(zipFileFullPath)
.Entries.Where(x => x.Name.Equals(targetFileName,
StringComparison.InvariantCulture))
.FirstOrDefault()
.Open(), Encoding.UTF8)
.ReadToEnd())
.ToArray());

the following code can read specific file as byte array :
using ZipArchive zipArchive = ZipFile.OpenRead(zipFilePath);
foreach(ZipArchiveEntry zipArchiveEntry in zipArchive.Entries)
{
if(zipArchiveEntry.Name.Equals(fileName,StringComparison.OrdinalIgnoreCase))
{
Stream stream = zipArchiveEntry.Open();
using MemoryStream memoryStream = new MemoryStream();
await stream.CopyToAsync(memoryStream);
return memoryStream.ToArray();
}
}

Zip files have a table of contents. Every zip utility should have the ability to query just the TOC. Or you can use a command line program like 7zip -t to print the table of contents and redirect it to a text file.

In such case you will need to parse zip local header entries. Each file, stored in zip file, has preceding Local File Header entry, which (normally) contains enough information for decompression, Generally, you can make simple parsing of such entries in stream, select needed file, copy header + compressed file data to other file, and call unzip on that part (if you don't want to deal with the whole Zip decompression code or library).

Extracting files from a Zip archive programmatically using C# and System.IO.Packaging

I have a bunch of ZIP files that are in desperate need of some hierarchical reorganization and extraction. What I can do, currently, is create the directory structure and move the zip files to the proper location. The mystic cheese that I am missing is the part that extracts the files from the ZIP archive.
I have seen the MSDN articles on the ZipArchive class and understand them reasonable well. I have also seen the VBScript ways to extract. This is not a complex class so extracting stuff should be pretty simple. In fact, it works "mostly". I have included my current code below for reference.
using (ZipPackage package = (ZipPackage)Package.Open(#"..\..\test.zip", FileMode.Open, FileAccess.Read))
{
PackagePartCollection packageParts = package.GetParts();
foreach (PackageRelationship relation in packageParts)
{
//Do Stuff but never gets here since packageParts is empty.
}
}
The problem seems to be somewhere in the GetParts (or GetAnything for that matter). It seems that the package, while open, is empty. Digging deeper the debugger shows that the private member _zipArchive shows that it actually has parts. Parts with the right names and everything. Why won't the GetParts function retrieve them? I'ver tried casting the open to a ZipArchive and that didn't help. Grrr.

If you are manipulating ZIP files, you may want to look into a 3rd-party library to help you.
For example, DotNetZip, which has been recently updated. The current version is now v1.8. Here's an example to create a zip:
using (ZipFile zip = new ZipFile())
{
zip.AddFile("c:\\photos\\personal\\7440-N49th.png");
zip.AddFile("c:\\Desktop\\2005_Annual_Report.pdf");
zip.AddFile("ReadMe.txt");
zip.Save("Archive.zip");
}
Here's an example to update an existing zip; you don't need to extract the files to do it:
using (ZipFile zip = ZipFile.Read("ExistingArchive.zip"))
{
// 1. remove an entry, given the name
zip.RemoveEntry("README.txt");
// 2. Update an existing entry, with content from the filesystem
zip.UpdateItem("Portfolio.doc");
// 3. modify the filename of an existing entry
// (rename it and move it to a sub directory)
ZipEntry e = zip["Table1.jpg"];
e.FileName = "images/Figure1.jpg";
// 4. insert or modify the comment on the zip archive
zip.Comment = "This zip archive was updated " + System.DateTime.ToString("G");
// 5. finally, save the modified archive
zip.Save();
}
here's an example that extracts entries:
using (ZipFile zip = ZipFile.Read("ExistingZipFile.zip"))
{
foreach (ZipEntry e in zip)
{
e.Extract(TargetDirectory, true); // true => overwrite existing files
}
}
DotNetZip supports multi-byte chars in filenames, Zip encryption, AES encryption, streams, Unicode, self-extracting archives.
Also does ZIP64, for file lengths greater than 0xFFFFFFFF, or for archives with more than 65535 entries.
free. open source
get it at
codeplex or direct download from windows.net - CodePlex has been discontinued and archived

From MSDN,
In this sample, the Package class is used (as opposed to the ZipPackage.) Having worked with both, I've only seen flakiness happen when there's corruption in the zip file. Not necessarily corruption that throws the Windows extractor or Winzip, but something that the Packaging components have trouble handling.
Hope this helps, maybe it can provide you an alternative to debugging the issue.
using System;
using System.IO;
using System.IO.Packaging;
using System.Text;
class ExtractPackagedImages
{
static void Main(string[] paths)
{
foreach (string path in paths)
{
using (Package package = Package.Open(
path, FileMode.Open, FileAccess.Read))
{
DirectoryInfo dir = Directory.CreateDirectory(path + " Images");
foreach (PackagePart part in package.GetParts())
{
if (part.ContentType.ToLowerInvariant().StartsWith("image/"))
{
string target = Path.Combine(
dir.FullName, CreateFilenameFromUri(part.Uri));
using (Stream source = part.GetStream(
FileMode.Open, FileAccess.Read))
using (Stream destination = File.OpenWrite(target))
{
byte[] buffer = new byte[0x1000];
int read;
while ((read = source.Read(buffer, 0, buffer.Length)) > 0)
{
destination.Write(buffer, 0, read);
}
}
Console.WriteLine("Extracted {0}", target);
}
}
}
}
Console.WriteLine("Done");
}
private static string CreateFilenameFromUri(Uri uri)
{
char [] invalidChars = Path.GetInvalidFileNameChars();
StringBuilder sb = new StringBuilder(uri.OriginalString.Length);
foreach (char c in uri.OriginalString)
{
sb.Append(Array.IndexOf(invalidChars, c) < 0 ? c : '_');
}
return sb.ToString();
}
}

From "ZipPackage Class" (MSDN):
While Packages are stored as Zip files* through the ZipPackage class, all Zip files are not ZipPackages. A ZipPackage has special requirements such as URI-compliant file (part) names and a "[Content_Types].xml" file that defines the MIME types for all the files contained in the Package. The ZipPackage class cannot be used to open arbitary Zip files that do not conform to the Open Packaging Conventions standard.
For further details see Section 9.2 "Mapping to a ZIP Archive" of the ECMA International "Open Packaging Conventions" standard, http://www.ecma-international.org/publications/files/ECMA-ST/Office%20Open%20XML%20Part%202%20(DOCX).zip (342Kb) or http://www.ecma-international.org/publications/files/ECMA-ST/Office%20Open%20XML%20Part%202%20(PDF).zip (1.3Mb)
*You can simply add ".zip" to the extension of any ZipPackage-based file (.docx, .xlsx, .pptx, etc.) to open it in your favorite Zip utility.

I was having the exact same problem! To get the GetParts() method to return something, I had to add the [Content_Types].xml file to the root of the archive with a "Default" node for every file extension included. Once I added this (just using Windows Explorer), my code was able to read and extract the archived contents.
More information on the [Content_Types].xml file can be found here:
http://msdn.microsoft.com/en-us/magazine/cc163372.aspx - There is an example file below Figure 13 of the article.
var zipFilePath = "c:\\myfile.zip";
var tempFolderPath = "c:\\unzipped";
using (Package package = ZipPackage.Open(zipFilePath, FileMode.Open, FileAccess.Read))
{
foreach (PackagePart part in package.GetParts())
{
var target = Path.GetFullPath(Path.Combine(tempFolderPath, part.Uri.OriginalString.TrimStart('/')));
var targetDir = target.Remove(target.LastIndexOf('\\'));
if (!Directory.Exists(targetDir))
Directory.CreateDirectory(targetDir);
using (Stream source = part.GetStream(FileMode.Open, FileAccess.Read))
{
FileStream targetFile = File.OpenWrite(target);
source.CopyTo(targetFile);
targetFile.Close();
}
}
}
Note: this code uses the Stream.CopyTo method in .NET 4.0

I agree withe Cheeso. System.IO.Packaging is awkward when handling generic zip files, seeing as it was designed for Office Open XML documents. I'd suggest using DotNetZip or SharpZipLib

(This is basically a rephrasing of this answer)
Turns out that System.IO.Packaging.ZipPackage doesn't support PKZIP, that's why when you open a "generic" ZIP file no "parts" are returned. This class only supports some specific flavor of ZIP files (see comments at the bottom of MSDN description) used among other as Windows Azure service packages up to SDK 1.6 - that's why if you unpack a service package and then repack it using say Info-ZIP packer it will become invalid.