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

Question

Is there anyway in  Net  C   to extract data from a zip file without decompressing the complete file   Simply I possibly want to extract data  file  from the start of a zip file  obviously this depends if the compression algorithm compress the file in a deterministic order

User · Answer

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

User · Answer

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

User · Answer

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   amp  amp   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

User · Answer

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   gt  x Name Equals targetFileName                                            StringComparison InvariantCulture                 FirstOrDefault                 Open    Encoding UTF8                ReadToEnd                  ToArray

User · Answer

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

User · Answer

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

[c#] How to read data from a zip file without having to unzip the entire file

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