Extracting files from an .APPV file with PowerShell

Whilst doing a lot of work with App-V 5.0 we have come across the requirement to look inside the .appv file with PowerShell. In our particular instance we’re after the package VersionId which is contained in the AppxManifest.xml file. As previously championed, we love automating and this should be easy!

The .appv file extension is a compressed archive and therefore, should be simple to crack open. After scouring the interweb, there is very little information on how to achieve this in code. We could use the built-in Shell32.dll functionality but this requires us to rename the file to .zip first. Ideally we want to avoid copying or renaming the source files. I did find one reference over on the Login Consultants forum which pointed me in the right direction.

Disclaimer: the following code requires the .Net Framework 4.5. The System.IO.Compression.FileSystem object is not available in previous releases. You can check in the C:\Windows\Microsoft.NET\assembly\GAC_MSIL\ folder and if you have the System.IO.Compression.FileSystem folder you should be good to go Smile with tongue out.

To get this new .Net functionality to work within PowerShell we will be calling the .Net assemblies directly and therefore need to create a couple of references. In our example we’ll be using both the System.IO.Compression and System.IO.Compression.FileSystem assemblies (two different DLLs hence the two references):

### The System.IO.Compression.FileSystem requires at least .Net Framework 4.5
[System.Reflection.Assembly]::LoadWithPartialName("System.IO.Compression") | Out-Null;
[System.Reflection.Assembly]::LoadWithPartialName("System.IO.Compression.FileSystem") | Out-Null;

Next we can create our FileStream object (with read only access) required by the ZipArchive object class.

### Open the ZipArchive with read access
$FileStream = New-Object System.IO.FileStream($SourceAppV5Archive, [System.IO.FileMode]::Open);
$AppV5Archive = New-Object System.IO.Compression.ZipArchive($FileStream);

In fact we can shorten this down to a single line:

### Open the ZipArchive with read access
$AppV5Archive = New-Object System.IO.Compression.ZipArchive(New-Object System.IO.FileStream($SourceAppV, [System.IO.FileMode]::Open));

Once we have opened our .ZIP (.appv) file we can retrieve the AppXManifest.xml file entry:

### Locate the AppxManifest.xml file
$AppxManifestEntry = $AppV5Archive.GetEntry("AppxManifest.xml");

Having the ZipArchiveEntry object we can extract it with the ExtractToFile method:

### Extract the $ZipArchiveEntry
$ZipArchiveEntry.ExtractToFile($SaveAs);

Unfortunately this does work and reports the following error:

Method invocation failed because [System.IO.Compression.ZipArchiveEntry] doesn't contain a method named 'ExtractToFile'.

Eh!? WT… Looking on the ZipArchiveEntry reference page on MSDN, the ExtractToFile is an Extension Method. Therefore, we need to utilise the underlying object method, the ZipFileExtensions.ExtractToFile method. For more information on Extension Methods in PowerShell see here and here. Now our code should look like this:

### Extract the ZipArchiveEntry (ZipArchiveEntry.ExtractToFile is an extension method)
[System.IO.Compression.ZipFileExtensions]::ExtractToFile($AppxManifestEntry, $SaveAs, $Overwrite);

Finally we need to ensure that we correctly dispose of the ZipArchive object otherwise we’ll leave it open:

### Ensure we close the file handle otherwise the file will be left open
$AppV5Archive.Dispose();

That’s it! It you want a simpler way of doing this, just download the Virtual Engine App-V 5.0 Package PowerShell CmdLets. You can achieve all this in just a single command:

Save-AppV5FileXml -AppV c:\package.appv -XML AppxManifest

Full PowerShell Code Snippet

Here is the full code listing:

### The System.IO.Compression.FileSystem requires at least .Net Framework 4.5
[System.Reflection.Assembly]::LoadWithPartialName("System.IO.Compression") | Out-Null;
[System.Reflection.Assembly]::LoadWithPartialName("System.IO.Compression.FileSystem") | Out-Null;

### Open the ZipArchive with read access
$AppV5Archive = New-Object System.IO.Compression.ZipArchive(New-Object System.IO.FileStream($SourceAppV5Archive, [System.IO.FileMode]::Open));

### Locate the AppxManifest.xml file
$AppxManifestEntry = $AppV5Archive.GetEntry("AppxManifest.xml");
### ZipArchiveEntry.ExtractToFile is an extension method
[System.IO.Compression.ZipFileExtensions]::ExtractToFile($AppxManifestEntry, $SaveAs, $true);

### Ensure we close the file handle otherwise the file will be left open
$AppV5Archive.Dispose();

1 Comment

Trackbacks & Pingbacks

  1. Extract SequencerVersion from .appv file | Sander Vis' Blog March 1, 2015 (9:10 pm)

    […] However, I only used them for inspiration. With all due respect, I didn’t want to use an extra module. Elsewhere on the Virtual Engine site, I found a blog by Iain about extracting files from an .appv with powershell. […]

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