Windows Integration Errors

How to Fix VSTO Add-In Error 0x80070002 During .NET Assembly Loading

Algirdas Jasaitis Oct 7, 2026 868 views

Question details

The user needs to resolve an issue where a VSTO add-in fails to load due to a .NET assembly dependency error.

How to Fix VSTO Add-In Error 0x80070002 During .NET Assembly Loading

Product: VSTO Add-In
Device & OS: Windows
Scenario: Running a VSTO add-in in a virtual desktop environment using FSLogix or with strict endpoint security software.
Observed behavior: The add-in fails to load, generating a Fusion log error 0x80070002 even when the primary DLL is present, often due to excluded or corrupted assembly paths.

Before you start

Ensure you have administrative access to the virtual desktop environment and the FSLogix configuration files before making modifications. It is also recommended to temporarily disable endpoint security software to isolate the cause.

Solution 1Recommended

Remove Assembly Cache Path from FSLogix redirections.xml

Prevents the assembly cache path from being excluded and corrupted upon sign-in in a virtual desktop environment.

In virtual desktop environments, FSLogix profile redirection can cause the AppData\Local\assembly\dl3 path to be excluded from the profile container. Modifying the redirections.xml file ensures the .NET assembly cache is maintained correctly across sessions.

Access FSLogix Configuration

Navigate to your default FSLogix Profile Container configuration folder on the file server or virtual machine.

Edit redirections.xml

Open the redirections.xml file using a text editor like Notepad with administrator privileges.

Remove Excluded Path

Locate and delete the entry for AppData\Local\assembly\dl3 from the file.

Apply Changes

Save the XML file and restart the virtual desktop session to apply the changes.

Remove Assembly Cache Path from FSLogix redirections.xml

Configuration Updated: Removing this path ensures the VSTO add-in dependencies are properly loaded from the profile container without corruption.

Solution 2

Whitelist .NET Assemblies in Cybersecurity Software

Resolves loading blocks caused by strict endpoint security policies interfering with .NET Framework execution.

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Frequently Asked Questions

What causes the 0x80070002 error when loading a VSTO add-in?

This error usually indicates that a required .NET assembly or dependent DLL could not be found, often due to profile virtualization exclusions or security software blocking the file.

Why does FSLogix cause issues with VSTO add-ins?

If the FSLogix redirections.xml file excludes the AppData\Local\assembly\dl3 folder, the assembly cache path is not saved in the profile container and becomes corrupted on the next login.

How can I check if my antivirus is blocking the VSTO add-in?

You can review the Fusion logs using the Assembly Binding Log Viewer (Fuslogvw.exe) to see if access is denied, or temporarily disable your security software in a test VM to see if the add-in loads successfully.

Do I need administrative privileges to edit the redirections.xml file?

Yes, editing the FSLogix Profile Container configuration files requires local administrator or domain administrator privileges, depending on your virtual desktop infrastructure.

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