'Error parsing app package' error after version change

Occasional Contributor

I integrated MSIX into a WinForms project and configured it as a package bundle and deployed to an Azure App Service.


Everything works fine and I can install the app. But when I deploy a new version it fails to auto update and when I try to install the application again it fails with "Error parsing app package" error.

If I sign out or restart my PC, it works. I'm not sure what to do to solve this, because the installer works. How can I solve this?


It looks like a caching issue or something similar, as described here. The Delivery Optimization Service doesn't download the entire App Installer file and because of this it fails to parse it.


I even tried the suggested workaround - to pad the contents of the App Installer file. But still doesn't work.


Not sure what else can I do here.

This is my App Installer file. I removed sensitive information so the urls will not work.

<?xml version="1.0" encoding="utf-8"?>
Version="" xmlns="">
Uri="" />
HoursBetweenUpdateChecks="0" />


This is my web.config in the Azure App Service:



<?xml version="1.0" encoding="utf-8"?>
<mimeMap fileExtension=".msix" mimeType="application/msix" />
<mimeMap fileExtension=".msixbundle" mimeType="application/msixbundle" />
<mimeMap fileExtension=".appx" mimeType="application/" />
<mimeMap fileExtension=".appxbundle" mimeType="application/" />
<mimeMap fileExtension=".appinstaller" mimeType="application/xml" />
<add name="Pragma" value="no-cache" />
<add name="Cache-Control" value="max-age=0, no-cache, no-store, must-revalidate" />
<add name="Expires" value="Sat, 01 Jan 2000 00:00:00 GMT"/>


4 Replies
best response confirmed by szilardd (Occasional Contributor)
Thanks @MikeH. This is in line with the workaround mentioned here:

I had implemented the workaround but there was an issue in the way I did the padding - which is now fixed and looks to work.
Great. The thread has a little bit of PowerShell on it that can be used to do the padding.