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name: solidworks-cad-addin-iswaddin description: 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. version: 1.0.0 tags:

• solidworks
• sldworks
• api
• add-in
• iswaddin
• csharp
• com

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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)

• Add-in creation routes (templates/wizards): https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Overview/SolidWorks_API_Add-Ins,_Project_Templates,_and_Wizards.htm?id=1.2.3.0
• Use .NET add-in templates: https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Overview/SolidWorks_CSharp_and_VB.NET__Project_Templates.htm?id=1.2.3.1
• Manual “SwAddin” approach (ISwAddin + registry): https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Overview/Using_SwAddin_to_Create_a_SolidWorks_Addin.htm?id=1.2.3.5
• CommandManager & command groups: https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/CommandManager_and_CommandGroups.htm?id=e695b1d69d874993be07528d907b2e75
• Callback/enable method signatures: https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Callbacks.htm
• Scaled add-in icons: https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Icons.htm
• Toolbar behavior/IDs: https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Toolbars.htm
• Concrete reference implementation (C#): https://help.solidworks.com/2025/english/api/sldworksapi/Create_TaskPaneView_Add-in_Example_CSharp.htm

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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:

• Install the SOLIDWORKS API SDK templates (the docs reference running SOLIDWORKS API SDK.msi from the SOLIDWORKS installation’s apisdk folder):
  https://help.solidworks.com/2025/english/api/sldworksapi/Create_TaskPaneView_Add-in_Example_CSharp.htm

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

Use the SOLIDWORKS API SDK add-in template:

• SwCSharpAddin (C#) or SwVBAddin (VB.NET) per:
  https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Overview/SolidWorks_CSharp_and_VB.NET__Project_Templates.htm?id=1.2.3.1

2) Ensure COM visibility + identity

In your main add-in class (commonly SwAddin):

• Ensure [ComVisible(true)]
• Ensure a stable [Guid("...")] (new GUID per add-in)
• Ensure [SwAddin(Description=..., Title=..., LoadAtStartup=...)] is present (as shown in the C# TaskPaneView example):
  https://help.solidworks.com/2025/english/api/sldworksapi/Create_TaskPaneView_Add-in_Example_CSharp.htm

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”):

• Register via:
  • Regsvr32.exe (unmanaged C++ and managed C++/CLI add-ins)
  • RegAsm.exe (C# and VB.NET add-ins)
    https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Overview/Using_SwAddin_to_Create_a_SolidWorks_Addin.htm?id=1.2.3.5

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:

• ISldWorks::SetAddinCallbackInfo (SOLIDWORKS “holds onto this object and makes callbacks”)
• ISldWorks::AddMenuItem3
• ISldWorks::AddToolbar4
  https://help.solidworks.com/2025/english/api/sldworksapiprogguide/Overview/Using_SwAddin_to_Create_a_SolidWorks_Addin.htm?id=1.2.3.5

The C# TaskPaneView example shows calling:

• iSwApp.SetAddinCallbackInfo(0, this, addinID);
  https://help.solidworks.com/2025/english/api/sldworksapi/Create_TaskPaneView_Add-in_Example_CSharp.htm

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

Use:

• ISldWorks::GetCommandManager to get the one ICommandManager instance
• Create one or more ICommandGroups 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:

• No parameters
• One string parameter (supported in SOLIDWORKS 2012 SP0+)
  https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Callbacks.htm

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:

• .NET templates include default icons of various sizes
• A post-build event renames them to match the DLL name and puts them next to the DLL
• You can replace the default icons with your own scaled icon set
  https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Icons.htm

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:

• First run “instantiates” toolbars and stores toolbar IDs in the registry
• During development, you may need to clear relevant registry entries before changing toolbar structure
• For release versions, assign new toolbar IDs to avoid collisions across versions
  https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/Add-in_Toolbars.htm

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

• HKEY_CURRENT_USER\Software\SOLIDWORKS\SOLIDWORKS <version>\User Interface\Custom API Toolbars\<index>
• HKEY_CURRENT_USER\Software\SOLIDWORKS\SOLIDWORKS <version>\User Interface\Toolbars\...
  https://help.solidworks.com/2025/English/api/sldworksapiprogguide/Overview/CommandManager_and_CommandGroups.htm?id=e695b1d69d874993be07528d907b2e75

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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=

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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.