Revit 2025 Debugger Error: Switching to Managed (CoreCLR) Debugger for .NET Framework 4.8.1 Project

[WALIDGIO]

Hi everyone,

I'm working on a Revit API plugin targeting .NET Framework 4.8.1. When I try to debug, I encounter the following error:

"A fatal error has occurred and debugging needs to be terminated. The debugger was configured to use the Desktop CLR (.NET Framework) Managed debugger, but the target process loaded the CoreCLR (.NET Core) runtime. To debug this project, configure it to use the 'Managed (CoreCLR)' debugger."

I’ve verified that the project is targeting .NET Framework 4.8.1, and I’ve set the correct references. However, I can’t find how to configure the debugger to use Managed (CoreCLR), as suggested by the error.

Has anyone faced this issue? Any guidance on how to resolve it would be greatly appreciated!

Thank you in advance.

here screenshot

Here the steps :

i followed the instruction but still have the error

[mdb]

Hi walidgio,

Revit 2025 no longer supports the .NET Framework for API development. Autodesk has transitioned to using .NET Core (more specifically, .NET 6 and beyond), best pick the highest possible,for Revit starting with recent releases. This shift aligns with the broader movement in the software industry, as .NET Framework is now considered a legacy technology and is no longer being actively developed by Microsoft.

To develop add-ins or integrations for Revit 2025, you'll need to use .NET Core/.NET 6. If you have existing .NET Framework-based projects, you'll need to migrate them to .NET Core/.NET 6. Fortunately, tools like the Portability Analyzer and the Upgrade Assistant can help you identify and address compatibility issues during the migration process.

Let me know if you need guidance on the migration or setting up your development environment for .NET Core and Revit 2025!

Cheers,

[WALIDGIO]

Hi mdb,

Thank you for the detailed explanation regarding the transition to .NET Core/.NET 6 for Revit API development.

I'm a beginner in Revit API development, and it just so happens that I started learning about it right when Autodesk decided to shift to .NET Core. This change has made things a bit challenging, as I’ve noticed the official documentation doesn’t yet provide a clear step-by-step guide for setting up a new project in this new environment.

If you could kindly guide me through the process of setting up a project step by step in .NET Core/.NET 6 for Revit 2025, it would be incredibly helpful. I want to make sure I’m starting off on the right foot with this new approach.

Thank you so much for your help!

Cheers,

[ricaun · Accepted solution]

The first step should be 'Class Library' without the (.NET Framework) and select .NET 8.0 that the version Revit 2025 uses.

I have some content about the transition about Revit to NET Core:

• https://ricaun.com/revit-api-net-core/

And here is the Migrating from .NET 4.8 to .NET Core 8 in the Jeremy blog.

• https://thebuildingcoder.typepad.com/blog/2024/04/migrating-from-net-48-to-net-core-8.html