COM Interop and AutoCAD 2025

[s3b79]

Hello,

I've just started a new job and my first task is to migrate an AutoCAD application written in .Net Framework / VB.NET to Autocad 2025 and therefore .Net 8.

This application is quite old and a large portion of the code still uses COM interop classes rather than managed classes. A line like

Dim blocTemps As New AcadBlockReference

works in .Net Framework but no longer works in .Net 8 : BC30517 Overload resolution failed because no 'New' is accessible.

Has anyone ever encountered this problem and could give me some advice on how to solve it?

Thanks in advance

[_gile]

Did you reference the AutoCAD 2025 libraries for AcDbMgd, AcCoremgd, AcMgd, Autodesk.AutoCAD.Interop, Autodesk.AutoCAD.Interop.Common, ... (version 25.0.58.0.0)?

[s3b79]

Yes, I am using the NuGet packages AutoCAd.NET (25.0.1)
and AutoCAD.NET.Interop (2025.25.0.58).

Visual Studio does recognize AutoCAD types.

[_gile]

You should provide more informations. For example, did you start a new project from scratch or upgrade an existing .NET Framework project with the .NET Upgrade Assistant? In the second case, you could read this topic.

[s3b79]

I did use the .NET Upgrade Assistant extension to update my projects.

But your comment was interesting. I tried to make a new project in .Net 4.7 and .Net 8.

I used this time NuGet packages to reference the classic AutoCAD libraries and local references for the interop libraries (because AutoCAD.NET.Interop is not an official package).

I read your doc but it didn't give me any clues, but thanks for that.

[_gile · Accepted solution]

Sorry, I'm not familiar with VB specifics and I try to avoid using COM interop in .NET plugins, but the code you posted doesn't make sense to me (i.e. creating an AcadBlockReference with New). As far as I know, you can only create a new AcadBlock reference with the InsertBlock method.

[s3b79]

I'm a C# guy too and I don't really like VB. but it's historical in the project where VBA code was migrated to VB.NET with interop.

I also wondered if it made sense to do a New. Maybe the New is useless because the reference is overwritten later and just declaring a variable of type AcadBlockReference without the new would be sufficient.

My project is big and I have many errors of this type to correct but I can try...

Thanks for your help.

[_gile]

I had to do this kind of migration a dozen years ago and I'm glad that today projects are entirely converted to C# without any reference to COM interop.

All the best.

[ActivistInvestor]

I would never write code that has a dependence on COM Interop. 

I have code that uses the COM API (e.g., AcadDocument), but does so via late-binding using System.Dynamic.

[Ed__Jobe]

Do you start development by referencing COM.Interop, just to get Intelisense and then switch to late binding when you're done?

[ActivistInvestor]

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@Ed__Jobe wrote:

Do you start development by referencing COM.Interop, just to get Intelisense and then switch to late binding when you're done?

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No, I go from memory, and I don't really do use COM very much to begin with, so not having Intellisense isn't really an issue.

[Ed__Jobe]

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@ActivistInvestor wrote:

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@Ed__Jobe wrote:

Do you start development by referencing COM.Interop, just to get Intelisense and then switch to late binding when you're done?

---

No, I go from memory, and I don't really do use COM very much to begin with, so not having Intellisense isn't really an issue.

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Thx. My memory isn't as good. So I have a shortcut to the help file. 🙂 However, if @s3b79 isn't familiar with the COM api and needs Intellisense, they should know that they have the option to set a reference to AutoCAD.COM.Interop and remove it before they compile for Release.

[s3b79]

As I said above, I have just taken over the maintenance of a project. This project uses interop classes (in addition to managed classes...). And it's not a choice, it's a fact.

I'm a developer and my knowledge of Autocad and its APi is very limited. @_gile's answer about the fact that the code I posted didn't make sense was very pertinent. I simply deleted the New and the code compiled.

I can't say that the migration to .Net 8 is complete, but this particular point seems to have been resolved.

Thanks to all.