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solidworks-cad-addin-iswaddin

Create a SOLIDWORKS (CAD) desktop add-in using the SOLIDWORKS API SDK templates or by implementing ISwAddin/SwAddin manually; includes COM/registry registration, ConnectToSW/DisconnectFromSW lifecycle, CommandManager UI, callbacks, icons, and toolbar considerations.

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manifest: skills/solidworks-cad-addin-iswaddin.skill.md
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SOLIDWORKS CAD add-in (ISwAddin) — create, register, and wire UI

When to use this skill

Use when you need to create a SOLIDWORKS desktop add-in (loaded by SOLIDWORKS itself; not a PDM vault add-in), implemented as a COM-visible DLL that SOLIDWORKS loads via ISwAddin.

What you should produce (outputs)

  • A C# (or VB.NET / C++/CLI / C++) add-in project that:
    • Implements 
      SolidWorks.Interop.swpublished.ISwAddin
      (
      ConnectToSW
      , 
      DisconnectFromSW
      )
    • Registers itself so it appears in Tools > Add-ins...
    • Adds at least one command (menu/toolbar/CommandManager) with correct callback/enable signatures
    • Has proper icons (including scaled icons if using .NET templates)

Authoritative documentation (SOLIDWORKS 2025)

Step-by-step: create the project (recommended: .NET template)

0) Install the SOLIDWORKS API SDK templates

Follow the “Create Task Pane View Add-in Example (C#)” prerequisites:

1) Create a new add-in project in Visual Studio

Use the SOLIDWORKS API SDK add-in template:

2) Ensure COM visibility + identity

In your main add-in class (commonly 

SwAddin
):

3) Implement COM registration that SOLIDWORKS uses to find your add-in

SOLIDWORKS add-ins must be registered as COM servers and then listed under the SOLIDWORKS add-in registry key (see “Using SwAddin to Create a SOLIDWORKS Add-In”):

For .NET add-ins, use 

[ComRegisterFunction]
/ 
[ComUnregisterFunction]
to create/remove the keys (the TaskPaneView example shows exactly what SOLIDWORKS expects):

  • HKLM: 
    HKEY_LOCAL_MACHINE\SOFTWARE\SolidWorks\Addins\{GUID}
    • Default value: 
      0
      (or 
      1
      to enable in Add-in Manager per SwAddin doc)
    • Description
      : string (shown in Add-in Manager)
    • Title
      : string (shown in Add-in Manager)
  • HKCU: 
    HKEY_CURRENT_USER\Software\SolidWorks\AddInsStartup\{GUID}
    • Default value: DWORD 
      0/1
      controlling load-at-startup (
      LoadAtStartup
      )

Reference code pattern (from the TaskPaneView add-in example): https://help.solidworks.com/2025/english/api/sldworksapi/Create_TaskPaneView_Add-in_Example_CSharp.htm

Important: writing HKLM requires elevated permissions on Windows; plan your install story accordingly (admin install or installer writes keys).

4) Implement ISwAddin lifecycle correctly

Implement:

  • bool ConnectToSW(object ThisSW, int Cookie)
    (called when the add-in is loaded)
  • bool DisconnectFromSW()
    (called when SOLIDWORKS is closing or the add-in is disabled)

In 

ConnectToSW
, the SwAddin manual notes you can call:

The C# TaskPaneView example shows calling:

5) Add UI: CommandManager + CommandGroups (recommended pattern)

Use:

  • ISldWorks::GetCommandManager
    to get the one 
    ICommandManager
    instance
  • Create one or more 
    ICommandGroup
    s via 
    ICommandManager::CreateCommandGroup
  • Add commands via 
    ICommandGroup::AddCommandItem2
  • Activate via 
    ICommandGroup::Activate

This is covered in: https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/CommandManager_and_CommandGroups.htm?id=e695b1d69d874993be07528d907b2e75

Callback + enable method signatures (critical)

Your menu/toolbar command callbacks and enable methods must use one of the supported signatures:

6) Icons: provide scaled icons (especially for .NET templates)

SOLIDWORKS Add-in Manager shows an icon next to your add-in name, and supports scaled icons (as of SOLIDWORKS 2022). The docs describe:

The Add-in Icons doc references scaled sizes (example set): 16, 20, 32, 40, 64, 96, 128 (e.g., 

MySwAddin_20.png
, 
MySwAddin_40.png
, etc.).

If you don’t place icons beside the DLL, the doc describes setting an 

Icon
value under the add-in registry key (e.g., 
HKEY_LOCAL_MACHINE\SOFTWARE\SOLIDWORKS\AddIns\{CLSID}\Icon
), with version-specific variants:
https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Icons.htm

7) Toolbars: handle toolbar IDs during development vs release

The toolbar docs explain:

The CommandManager doc calls out where toolbar definitions live and how to remove them, e.g.:

Packaging/deployment (Windows Installer)

If you need a deployable installer, follow: https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Miscellaneous/Create_Setup_Project_to_Distribute_SolidWorks_Add-in.htm?format=P&value=

Debug checklist (pragmatic)

  1. Confirm COM registration succeeds (for .NET, 
    regasm /codebase
    -style workflows or installer; for unmanaged, 
    regsvr32
    ).
  2. Confirm registry keys exist: 
    • HKLM\SOFTWARE\SolidWorks\Addins\{GUID}
    • HKCU\Software\SolidWorks\AddInsStartup\{GUID}
  3. Start SOLIDWORKS → Tools > Add-ins... and confirm:
    • Add-in appears with correct Title/Description
    • Load-at-startup behavior matches expectation
  4. Attach debugger to 
    sldworks.exe
    , set breakpoints in 
    ConnectToSW
    and your command callbacks.
  5. If UI commands don’t show, verify CommandGroup IDs/activation logic per CommandManager guide, and reset toolbar registry entries during development as needed.