The process of preparing an application for MSIX app attach follows a specific sequence.

1. First, a signing certificate must be generated (or obtained). All MSIX packages must be digitally signed to be trusted by the operating system.
2. Next, you use the MSIX Packaging Tool to capture the application installer (App1) and create an MSIX package (a .msix file). During this process, the package is signed using the certificate from the first step.
3. Then, the signed .msix package file must be expanded into a virtual disk format. This step creates an MSIX image (a VHD, VHDX, or CIM file) using a tool like msixmgr.exe.
4. Finally, this resulting MSIX image file (not the package) is uploaded to the Azure file share (Share1), making it accessible to the AVD host pool for mounting.

"Generate an encryption certificate" is incorrect as a signing certificate is required, not an encryption one. "Upload the MSIX package" is incorrect because the expanded disk image is uploaded, not the base .msix package.

Microsoft Learn (Azure Virtual Desktop documentation): "Create an MSIX image to use with App Attach in Azure Virtual Desktop"

Reference: This document outlines the prerequisites and steps. It explicitly states that you need an "MSIX-packaged application (.msix file)" before you can run the msixmgr tool to "create an MSIX image." It also shows the msixmgr.exe -Unpack command which takes a .msix package as input and outputs a VHD, VHDX, or CIM file.

Microsoft Learn (MSIX documentation): "Create a certificate for package signing"

Reference: This document details the necessity of signing and how to create a self-signed certificate (e.g., using the New-SelfSignedCertificate PowerShell cmdlet). It states, "All MSIX and Appx application packages include a certificate. You're responsible for making sure the certificates are trusted in your environment." This confirms generating a certificate is a required step.

Microsoft Learn (MSIX documentation): "Create an MSIX package from any desktop installer"

Reference: This guide on the MSIX Packaging Tool shows that during the creation of the package, there is a "Sign package" step where you must "select a .pfx certificate file." This confirms that the certificate must be available to complete the package creation, logically placing certificate generation before or concurrent with package finalization.