---
id: post/demiliani-com/12123
type: post
title: "Dynamics 365 Business Central on-prem: be careful when referencing .NET assemblies across versions."
summary: When upgrading Business Central on-premises and using custom extensions with .NET assemblies, ensure assemblies are compiled for .NET Standard if targeting version 21 or later, even if the AL compiler allows .NET Framework versions locally. The runtime requires .NET Standard compliance to publish successfully.
tier: community
language: en
tags:
  - on-premises
  - .net assemblies
  - extension publishing
  - version upgrade
  - net standard
  - add-ins
system: platform
review:
  state: reviewed
  by: opus
  at: "2026-10-08T02:00:07.614Z"
  flags: []
generated:
  at: "2026-10-08T01:26:53.141Z"
  pipeline: 0.2.0
  prompts:
    extract-post: 1
  input_hash: d3e863fdd73255a9a2d93003b4fa5f9d9195c6c5ad945165f3f33e2071133e20
evidence:
  - kind: blog
    url: https://demiliani.com/2025/07/14/dynamics-365-business-central-on-prem-be-careful-when-referencing-net-assemblies-across-versions/
    title: "Dynamics 365 Business Central on-prem: be careful when referencing .NET assemblies across versions."
    date: "2025-07-14"
    commit: null
    t: null
    quote: null
links:
  learn: []
  objects: []
  features: []
  topics: []
  localizations: []
  videos: []
  posts: []
  guidelines: []
post_id: "12123"
source_id: demiliani-com
source_name: Stefano Demiliani
url: https://demiliani.com/2025/07/14/dynamics-365-business-central-on-prem-be-careful-when-referencing-net-assemblies-across-versions/
published_at: "2025-07-14T13:40:05.000Z"
author: Stefano Demiliani
full_text: false
words: 464
quotes: []
code_objects_mentioned: []
systems:
  - platform
  - development
  - administration
versions_mentioned:
  - "14"
  - "21"
  - "25"
preview:
  embeddable: true
  frame_url: https://demiliani.com/2025/07/14/dynamics-365-business-central-on-prem-be-careful-when-referencing-net-assemblies-across-versions/embed/
  image: https://demiliani.com/wp-content/uploads/2021/08/d365bclogowhite.jpg
  image_alt: null
  image_w: 394
  image_h: 362
  site_name: Stefano Demiliani
  favicon: https://demiliani.com/wp-content/uploads/2022/09/sd_wordpress_logo.png?w=32
  probed_at: "2026-10-07T11:51:55.243Z"
---

# Dynamics 365 Business Central on-prem: be careful when referencing .NET assemblies across versions.

[Read the post](https://demiliani.com/2025/07/14/dynamics-365-business-central-on-prem-be-careful-when-referencing-net-assemblies-across-versions/) · Stefano Demiliani (Stefano Demiliani, MVP) · 2025-07-14 · 464 words · tier community · reviewed (checked by Opus)

> When upgrading Business Central on-premises and using custom extensions with .NET assemblies, ensure assemblies are compiled for .NET Standard if targeting version 21 or later, even if the AL compiler allows .NET Framework versions locally. The runtime requires .NET Standard compliance to publish successfully.

## Key points

- Business Central version 21 and later only support .NET Standard compiled add-ins at runtime, not .NET Framework versions
- The AL compiler accepts both .NET Standard and .NET Framework assemblies during local compilation, masking compatibility issues
- Extensions must be compiled with .NET Standard assemblies when published to service tiers running version 21 or later
- Reload Visual Studio Code after updating assemblies in probing paths to avoid caching old assembly versions

## Context

- Features: .NET add-in support, .NET Standard runtime, assembly probing paths, extension publication
- Versions: 14, 21, 25

Source: Stefano Demiliani, community blog. Summary, key points and quotes are derived (CONTENT-NOTICE.md); read the original for the full text.