c# - How can I unzip a file to a .NET memory stream?

Question

I have files (from 3rd parties) that are being FTP'd to a directory on our server. I download them and process them even 'x' minutes. Works great.

Now, some of the files are .zip files. Which means I can't process them. I need to unzip them first.

FTP has no concept of zip/unzipping - so I'll need to grab the zip file, unzip it, then process it.

Looking at the MSDN zip api, there seems to be no way i can unzip to a memory stream?

So is the only way to do this...

1. Unzip to a file (what directory? need some -very- temp location ...)
2. Read the file contents
3. Delete file.

NOTE: The contents of the file are small - say 4k <-> 1000k.

Answer 1

Zip compression support is built in:

using System.IO;
using System.IO.Compression;
// ^^^ requires a reference to System.IO.Compression.dll
static class Program
{
    const string path = ...
    static void Main()
    {
        using(var file = File.OpenRead(path))
        using(var zip = new ZipArchive(file, ZipArchiveMode.Read))
        {
            foreach(var entry in zip.Entries)
            {
                using(var stream = entry.Open())
                {
                    // do whatever we want with stream
                    // ...
                }
            }
        }
    }
}

Normally you should avoid copying it into another stream - just use it "as is", however, if you absolutely need it in a MemoryStream, you could do:

using(var ms = new MemoryStream())
{
    stream.CopyTo(ms);
    ms.Position = 0; // rewind
    // do something with ms
}