Is it possible to change file content directly in zip file?

Question

I have form with text box and customer wants to store all changes from this textbox to zip archive.

I am using http://dotnetzip.codeplex.com and i have example of code:

 using (ZipFile zip = new ZipFile())
  {
    zip.AddFile("text.txt");    
    zip.Save("Backup.zip");
  }

And i dont want to create each time temp text.txt and zip it back. Can I access text.txt as Stream inside zip file and save text there?

Answer 1

There is an example in DotNetZip that use a Stream with the method AddEntry.

String zipToCreate = "Content.zip";
String fileNameInArchive = "Content-From-Stream.bin";
using (System.IO.Stream streamToRead = MyStreamOpener())
{
  using (ZipFile zip = new ZipFile())
  {
    ZipEntry entry= zip.AddEntry(fileNameInArchive, streamToRead);
    zip.Save(zipToCreate);  // the stream is read implicitly here
  }
}

A little test using LinqPad shows that it is possible to use a MemoryStream to build the zip file

void Main()
{
    UnicodeEncoding uniEncoding = new UnicodeEncoding();
    byte[] firstString = uniEncoding.GetBytes("This is the current contents of your TextBox");
    using(MemoryStream memStream = new MemoryStream(100))
    {
        memStream.Write(firstString, 0 , firstString.Length);
        // Reposition the stream at the beginning (otherwise an empty file will be created in the zip archive
        memStream.Seek(0, SeekOrigin.Begin);
        using (ZipFile zip = new ZipFile())
        {
            ZipEntry entry= zip.AddEntry("TextBoxData.txt", memStream);
            zip.Save(@"D:\temp\memzip.zip");  
        }
     }
}

Answer 2

There is another DotNetZip method accepting a file path as an argument:

   zip.RemoveEntry(entry);
   zip.AddEntry(entry.FileName, text, ASCIIEncoding.Unicode);