Migrating Your AutoCAD .NET Add-ins from 2023 to 2025 (.NET 8)

Migrating Your AutoCAD .NET Add-ins from 2023 to 2025 (.NET 8)

Shout-out to Imran Shaikh and everyone like him who asked for a practical, end-to-end guide on moving AutoCAD 2023 .NET automation into the AutoCAD 2025 and .NET 8 world. This article is for you.

AutoCAD 2025 is a turning point for desktop CAD automation. Under the hood, Autodesk has moved the managed API to .NET 8, which changes how we structure, compile, and load add-ins. The good news: you get access to modern C#, better performance, and long-term support. The risk: if you treat 2025 like “just another yearly upgrade,” your plugins will break.

This guide gives you breadth over depth—a migration framework, high-leverage features, and the main pitfalls to avoid—so you can get your 2023-era C# add-ins running confidently in AutoCAD 2025.

1. The 80/20 Migration Framework

Use this seven-step framework as your checklist. These are the 20% of decisions that drive 80% of your migration effort.

1. Inventory and classify your automations

   List each plugin/add-in: commands, dependencies, target products (AutoCAD, verticals), and whether it touches:

   • Managed .NET only

   • ObjectARX / C++/CLI wrappers

   • COM/ActiveX automation

   • AutoLISP/DCL

     
     

2. Set up the new toolchain

   Install:

   • AutoCAD 2025 (or your target vertical).

   • ObjectARX/Managed .NET SDK 2025.

   • Visual Studio 2022 (17.8 or later) + .NET 8 SDK.

   
   

3. Choose a project strategy

   • Upgrade existing projects in place using Microsoft’s Upgrade Assistant.

   • Or create new .NET 8 class libraries and copy code over (cleaner for long-term).

   
   

4. Retarget references to AutoCAD 2025

   Point to the 2025 managed assemblies (for example, AcMgd.dll, AcDbMgd.dll) from the 2025 SDK instead of the 2023 versions.

   
   

5. Handle breaking changes

   Fix API changes, COM interop differences, and any assumptions tied to .NET Framework 4.8.

   
   

6. Decide on backward compatibility

   Either:

   • Maintain a single multi-targeted solution (e.g., shared code + different build configurations).

   • Or branch your codebase by generation (2023-minus vs 2025+).

     
     

7. Test, profile, and package

   • Configure debug profiles that launch acad.exe 2025 with your add-in loaded.

   • Smoke-test commands, large drawings, and multi-document workflows.

   • Ship a clear installer/update story for your users.

   
   

2. What Actually Changed Between 2023 and 2025?

2.1 Runtime and SDK

• AutoCAD 2023 .NET add-ins typically target .NET Framework 4.8 using the 2023 managed SDK.

• AutoCAD 2025 introduces a .NET 8-based managed SDK. Autodesk’s compatibility table and managed .NET documentation confirm the move to the new runtime and SDK series for 2025.

The high-level API surface feels familiar (same namespaces, types, and patterns), but the hosting runtime and build system are different.

2.2 ObjectARX and Mixed Solutions

If you have C++/CLI wrappers or native ObjectARX modules, you must follow both:

• .NET Migration Guide (.NET 8) for managed components.

• ObjectARX Migration Guide for native modules and ARX/DBX binaries.

These guides describe version-specific changes, build settings, and binary compatibility expectations.

2.3 Automation and COM Interop

If your 2023 tools talk to AutoCAD via COM (e.g., AcadApplication through Marshal.GetActiveObject):

• .NET 8 removed some legacy COM helper APIs, so you may have to implement equivalent logic manually.

• Review any ActiveX automation projects against Autodesk’s “Migrating Automation Projects” guidance for 2025.

  
  

3. Setting Up a Clean .NET 8 AutoCAD 2025 Project

A clean, repeatable setup pays off quickly. Here is the high-level pattern that works well in practice.

3.1 Core Requirements

• Visual Studio 2022 (17.8+) with .NET 8 SDK.

• AutoCAD 2025 installed locally.

• ObjectARX 2025 SDK installed and extracted (for managed references and headers).

3.2 New Project Template (Recommended)

1. Create a Class Library project targeting .NET 8.0.

2. Add references to the 2025 managed assemblies from the ObjectARX SDK:

   • AcMgd.dll

   • AcDbMgd.dll

   • (Plus any vertical-specific assemblies you rely on.)

3. In the Debug profile, set:

   • Executable: path to acad.exe (your 2025 build).

   • Arguments: optional script to auto-load your DLL.

This mirrors the approach described in community migration guides and keeps your project layout future-proof.

3.3 Using the Upgrade Assistant (If You Prefer In-Place Migration)

If you want to upgrade an existing 2023 project:

• Use the Upgrade Assistant in Visual Studio to move the project from .NET Framework 4.x to .NET 8.

• After upgrading:

  • Re-point references to the 2025 SDK assemblies.

  • Re-create the debug profile for AutoCAD 2025.

  • Rebuild and run inside AutoCAD.

  
  

4. High-Leverage C# / .NET 8 Improvements for AutoCAD Add-ins

Once you are compiling against .NET 8, you can selectively adopt modern C# and BCL features that provide the most value for CAD automation:

• Records and immutable models for configuration and command parameters.

• Pattern matching and switch expressions for command routing and entity classification.

• async / await for non-UI tasks (I/O, web calls) that coordinate with long-running CAD operations.

• Dependency Injection for cleaner, testable command implementations; .NET 8 supports DI patterns out of the box, which you can wire into your add-in startup.

• Improved collections and Span<T>/Memory<T> for more efficient geometry processing and bulk entity operations.

You do not have to rewrite everything immediately. Apply the Pareto rule:

Start by modernizing the 20% of code that runs on every command or touches large selections—geometry, selection filters, data marshaling—because that is where .NET 8’s performance gains show up first.

5. Lesser-Known but Important Tips

These are the quieter details that can save you hours.

5.1 Reference from the SDK, Not the Installed Program Folder

It is tempting to reference DLLs directly from the AutoCAD installation directory, but Autodesk recommends referencing the assemblies from the ObjectARX SDK instead.

This avoids issues when a user has a different product flavor or updates their installation.

5.2 Separate Native and Managed Concerns

If you have both:

• Keep C++/CLI wrappers and C# add-ins in separate projects.

• Migrate C++/CLI using the ObjectARX migration guide and any 64-bit guidance if you still have older 32-bit assumptions.

5.3 Debug Profiles per Vertical

If you support multiple products (AutoCAD, Map 3D, Civil 3D):

• Create one debug profile per executable.

• Use launch scripts to load the same DLL with different configuration/behavior.

5.4 Guard Against API Surface Differences

Even if most namespaces are stable, do not assume 1:1 parity:

• Rebuild with warnings as errors to catch obsolete or changed members.

• Use compiler analyzers for nullable reference types and async best practices.

  
  

6. Things to Watch Out For (Pitfalls Checklist)

Before you declare migration “done,” walk through this list:

1. Runtime Assumptions

   • Remove any code that depends on AppDomain tricks or full-framework-only APIs.

   • Review COM interop code and re-implement helpers that were removed in .NET 8, such as Marshal.GetActiveObject.

     
     

2. Loading and Registration

   Verify your demand-loading registration or loader scripts against the 2025 documentation so your commands auto-load correctly.

   
   

3. Third-Party Dependencies

   Libraries compiled only for .NET Framework 4.x will not load into your .NET 8 add-in. Look for:

   • Updated .NET 6/7/8 versions.

   • Or isolate those capabilities behind COM/ActiveX or service calls.

   
   

4. Mixed AutoCAD Version Support

   If you still support 2020–2024, you may need:

   • Separate solutions/projects per generation, or

   • A multi-targeting layout as described in community migration articles.

   
   

5. Performance & Memory

   Use AutoCAD 2025 on large drawings to validate:

   • Selection performance.

   • Long-running commands that iterate lots of entities.

   • Where you see regressions, profile first—do not immediately blame .NET 8; sometimes a subtle logic change is the culprit.

     
     

7. Testing and Release Flow

A simple, repeatable release flow keeps your users confident:

1. Sandbox Profile

   • Create an AutoCAD 2025 profile that loads only your add-ins and test tool palettes.

2. Automated Smoke Tests

   • For each command, document:

     • Expected inputs (layers, entity types, DWG size).

     • Expected outputs (new entities, annotations, xdata, etc.).

   • Run these tests on a couple of representative projects before every release.

3. Logging and Diagnostics

   • Add structured logging (e.g., to JSON or ETW) around:

     • Command entry/exit.

     • Transactions and exceptions.

   • Make it easy for users to send you logs from failed sessions.

4. Deployment

   • Package your .NET 8 DLLs and configuration files with:

     • Clear instructions for the support and CAD admin teams.

   • If you are using installers, test:

     • Clean install.

     • Upgrade from previous 2023-era add-ins.

       
       

8. Essential Documentation & Learning Resources

When you want to go deeper than this overview, start here:

Autodesk Official Docs

• Managed .NET Developer’s Guide (AutoCAD 2025) – high-level API concepts and workflows.

• AutoCAD 2025 .NET Migration Guide – version-specific guidance for updating existing .NET add-ins.

• Managed .NET Compatibility Table – which managed SDK and .NET versions map to which AutoCAD releases.

• AutoCAD 2023 .NET Migration Guide – useful to understand where you are migrating from.

• ObjectARX Migration Guide (2025) – required reading if you use C++/CLI or native ARX modules.

• Migrating Automation Projects (ActiveX) – for VBA/COM-based workflows.

  
  

Community and Deep-Dive Guides

• TechSoft3D – “How to migrate an AutoCAD based application to .NET Core 8.0” (Part I & II) – detailed walkthroughs for mixed C++/CLI and fully managed apps, including multi-targeting strategies.

• QuuxSoft – “Update of a .NET (C#) project for AutoCAD 2025 (.NET 8.0)” – step-by-step PDF showing Visual Studio upgrade, debug profiles, and SDK referencing.

• Autodesk Webinar – “Autodesk Desktop API Updates: .NET Core 8.0 Migration” – official video walkthrough of migration concepts.

• AutoCAD API on Autodesk Platform Services (APS) – for future-proofing cloud workflows that complement your desktop add-ins.

  
  

9. Closing Thoughts

AutoCAD 2025 is not just “2023 plus features”; it is your entry point into a .NET 8, modern-C#, long-term-support world for CAD automation.

If you:

• inventory your add-ins,

• move them onto clean .NET 8 projects referencing the 2025 SDK,

• handle the COM/mixed-mode edge cases,

• and adopt a simple but disciplined test and deployment flow,

You will be ahead of most teams still treating this as a routine yearly upgrade.

Again, thank you to Imran Shaikh for pushing this topic. If you are working with AutoCAD, Revit, or other Autodesk APIs and want more migration guides like this—from the perspective of real engineering teams—reach out. CadGuardian exists for engineers exactly like you.