Dynamics NAV 2018 Client Add-in Cache
This article explains how Microsoft.NET add-ins are loaded in the Dynamics NAV Role Tailored client.
Add-in resolution order
The client resolves add-ins by checking locations in this order:
- Local client installation —
C:\Program Files (x86)\Microsoft Dynamics NAV\110\RoleTailored Client\Add-ins\ - Local user cache —
%LOCALAPPDATA%\Microsoft\Microsoft Dynamics NAV\110\Client\Add-ins\ - Server —
C:\Program Files\Microsoft Dynamics NAV\110\Service\Add-ins\
If the client finds the required DLL in the local installation folder, it uses that directly and never contacts the server for that add-in. The server-side version is ignored entirely.
Server-side storage
Add-ins not satisfied locally are served from the NAV Service tier:
C:\Program Files\Microsoft Dynamics NAV\110\Service\Add-ins\
Each add-in occupies its own subfolder containing the assembly DLL and any associated resources.
How the cache works
When a page requiring a control add-in is loaded and no local installation copy is found, the client compares the assembly version of the DLL on the server against the version of the DLL it has cached locally. If the versions differ — or no cache exists yet — the client copies the entire folder in which the matching DLL resides from the server down to the local cache. All sibling files (scripts, stylesheets, images, etc.) come along automatically as part of that folder copy.
Cache invalidation
There is no TTL. Invalidation is version-gated only: bump the assembly version of the DLL and every client will re-download the full add-in folder on next connect.
Common issues
| Problem | Cause | Fix |
|---|---|---|
| Server update has no effect on a specific machine | A locally installed copy of the DLL takes precedence | Check the client Add-ins\ installation folder and remove or update the local copy |
| Add-in works on one machine, not another | Per-user cache or local installation is in a different state | Clear the cache folder, or check for a locally installed version |
| "Could not load add-in" after a server upgrade | Service\Add-ins\ folder not carried over |
Re-deploy add-in folders to the new service installation |
| Add-in behaves inconsistently or loads the wrong version | The same DLL exists in multiple subfolders — the Add-ins folder is searched recursively to full depth, so the client picks whichever copy it encounters first, which is non-deterministic | Ensure each DLL exists in exactly one subfolder under Add-ins\ |
Clearing the user cache manually
Remove-Item "$env:LOCALAPPDATA\Microsoft\Microsoft Dynamics NAV\110\Client\Add-ins\*" -Recurse -Force
Close the NAV client before clearing — the next connection repopulates the cache from the server, unless a local installation copy is found first.
Important constraint
Control add-ins in NAV 2018 run as full-trust .NET assemblies inside the client process. A faulty add-in can crash the entire client, not just the control it hosts.