How to NETLOAD a .NET Plugin in AutoCAD
To load a .NET plugin in AutoCAD, type NETLOAD at the command line, browse to the .dll, and click Open. AutoCAD reflects over the assembly and registers every class marked with [CommandMethod]. To load on every AutoCAD startup, package the DLL as an AutoCAD .bundle or register it under HKCU\Software\Autodesk\AutoCAD\R<ver>\Applications.
Steps
Confirm the DLL targets your AutoCAD version
AutoCAD .NET plugins are version-locked to the AcDbMgd/AcMgd they were built against. A plugin built for AutoCAD 2024 may not load in 2025 without a rebuild. Check the seller's compatibility notes before loading.
Run NETLOAD
At the AutoCAD command line, type NETLOAD and press Enter. The Choose .NET Assembly dialog opens. Browse to your .dll and click Open.
Handle the security prompt
If the folder isn't in Trusted Locations, AutoCAD shows a security dialog. Click Load Once for a trial, or add the folder permanently under Options → Files → Trusted Locations and click Always Load.
Run the command
Type the command name added by the plugin (look for [CommandMethod("NAME")] in the source or seller's docs) and press Enter.
Set up auto-load (optional)
Drop the DLL into an AutoCAD .bundle folder, or add a registry key at HKCU\Software\Autodesk\AutoCAD\R<ver>\ACAD-<langID>\Applications\YourPlugin with LOADCTRLS=2, LOADER='C:\path\to\YourPlugin.dll'. AutoCAD auto-NETLOADs on next launch. Most commercial installers do this for you.
Frequently asked questions
I get 'Cannot load assembly'. What's wrong?
Three common causes: (1) the DLL targets a different AutoCAD version (rebuild against the correct AcDbMgd/AcMgd); (2) the DLL has unresolved dependencies — every referenced DLL must be in the same folder; (3) the DLL was downloaded over a network and Windows blocked it (right-click → Properties → Unblock).
Will NETLOAD warn me if a plugin is malicious?
AutoCAD only warns about untrusted load locations; it does not scan plugin code. Buy plugins from vendors that publish what's inside (e.g. CAD Exchange runs automated security scans on every uploaded DLL before listing). Never NETLOAD a DLL from an unknown source.
How do I unload a .NET plugin?
You can't. AutoCAD's .NET hosting does not support assembly unload — you have to close AutoCAD and reopen without loading the DLL.
Where does NETLOAD log errors?
AutoCAD writes load errors to the command line history (press F2 to see it). For deeper diagnostics, attach a debugger or check the Windows Event Viewer Application log.
Does NETLOAD work in AutoCAD LT?
No. AutoCAD LT does not host the .NET runtime. Plugin authors typically ship a LISP fallback for LT users, but the core .NET features won't be available.
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Related terms
The AutoCAD command that loads a managed .NET plugin DLL into the running session.
A managed assembly (C#/VB.NET DLL) that uses Autodesk's .NET API to add commands and behaviour to AutoCAD or Civil 3D.
The .NET attribute you place on a method to expose it as a typeable AutoCAD command after NETLOAD.
Two related AutoCAD mechanisms for loading plugins on demand: the (autoload) LISP function and the auto-load registry/bundle keys used for .NET DLLs.
AutoCAD's allow-list of folders that can load executable code (LISP, .NET, ARX) without a security warning.
Autodesk's C++ runtime extension SDK for AutoCAD. The lowest-level, highest-performance way to extend AutoCAD.